Bearing in mind that Evans was a very common name, the paragraphs below give a framework for guesswork
Mr Evans 15.5.1791 tea at Godwin's / 28.1.1794 Evans at Muir's === these two entries or either of them could have been Godwin's schoolfriend Richard Evans (qv)
3.2.1804 Evans at Hamilton Rowan's === see Joshua Evans 1824 below for one possible
8.1.1806 Evans at Joseph Johnson's / 6.11.1807 again ===
16.1.1806 Evanss at Jeremiah Joyce's ===
24.4.1809 Evans calls / 26.7.1809 call on Evans (Mullet) / 21.11.1809 call on Evans / 8.2.1810 Evans at tea / 22.3.1810 call on Evans / 5.6.1810 rev Evans calls /  8.6.1810 call on Evans / 30.6.1810 again / 23.1.1811 again /  18.4.1811 again / 19.6.1811 write to Evans / 20.6.1811 again / 21.6.1811 again / 25.10.1811 calls === Evans (Mullet) was perhaps Joseph Jeffries Evans merchant of St Mary Axe bapt Bristol 1768 son of Caleb & Sarah who married 23.2.1796 at St Botolph Bishopsgate Mary Ann Mullett with consent of her father Thomas Mullett (qv). Among their children were Frederic Mullet Evans printer 1804-1861 and Thomas Mullett Evans solicitor will PCC 1834 Bristol. Joseph Jeffries Evans was buried 31.12.1812 at Bunhill Fields, his will PCC 1813. I found a refernce (currently lost) to him as Rev Joseph Jeffries Evans. If he was a minister as well as a merchant all these 1809-1811 entries could have referred to him. John Evans DNB 1767-1827 was a Baptist minister and schoolmaster in London from 1795 to 1825, in Alan Ruston's unitarianhistory.org.uk he is noted as a Doctor of Laws (though the DNB doesn't mention this) so he could have been the rev Evans of 1810 and/or the dr Evans of 1821as well as some of the plain Evans entries
1.7.1813 Evans of Aldgate calls / 25.8.1813 call on Evans / 26.8.1813 again / 8.1.1814 John Evans (Bristol) au soir / 9.1.1814 Evans (Bristol) adv at dinner / 9.2.1814 write to Evans, Camberwell / 11.2.1814 call on Evans / 13.2.1814 again / 22.7.1814 again / 5.5.1815 Evans call, from Hamilton === Evans of Aldgate may have been J Evans linendraper of Aldgate bankrupt 1814 or John Evans will PCC 1829 grocer & tea dealer of 82 Aldgate. John Evans of Bristol could have been John Evans DNB 1784-1831 Unitarian minister and schoolmaster who was educated by John Prior Estlin (qv) or John Evans DNB 1774-1828 (at that time proprietor of the Bristol Mercury). Evans of Camberwell may have been John Clark Evans brewer of Camberwell Green & Peacocks Wharf, Montague Close, Southwark (Sun Fire 1807) who married 29.9.1810 at St Andrew's Holborn Sarah Dunster of Hertford, their children were baptised in Hertford in 1813 and 1814 and John Clark Evans seems to have been a brewery manager in Hertford in 1827 (reference lost) OR Edward Evans of Kent Road Camberwell will PCC 1830 a Yeoman of the Guard wife Mary Ann father Edward aunt Elizabeth Roberts aunt Catherine Marshall exec Wm Wear Marshall sister in law Elizabeth Vaux OR George Evans of Peckham Camberwell will PCC 1833 wife Mary (nee Mendham married 1782 St Stephen Walbrook their son Robert Mendham Evans died 1878 bapt 1803 Independent Chapel Tooting) brother in law John Mendham OR Sarah Evans widow of Camberwell will PCC 1831 late husband John Evans (who married 20.8.1801 of St John Zachary bach at Camberwell St Giles Sarah Gastineau otp sp and died 1805) There was also Ann Evans spinster of Camberwell will PCC 1805 sister Eleanor Peacock
17.2.1817 seek Evans / 18.2.1817 call on Evans / 19.2.1817 meet Evans / 1.6.1817 call on Evans, Dulwich / 15.6.1817 write to Evans / 16.11.1817 call on Evans / 4.12.1817 write to Evans / 13.12.1817 letter from Evans / 24.12.1817 call on Evans / 2.1.1818 write to Evans === Bodleian Abinger c42 f120v Godwin's letter to his wife of 2.6.1817 referred to his visit to Evans at Dulwich as on 1.6.1817 above. Godwin said that by an unlucky accident they had lost the East-India Chambers (mentioned in diary 12.5.1817) but that he still had two negotiations on foot, and had gone to Mr Evans in Dulwich (who was very encouraging) before dining with Walking Stewart and then going to see the other party after dinner., who, from the diary entry, must have been Turnbull, who appeared in the diary ten times in May and early June 1817. The only Evans I found in any way linked to Dulwich was John Evans 1787-1865 wholesale druggist of 62 Wood Street Cheapside, one of whose children was baptised in Dulwich in 1827
4.3.1820 Evans's, Pall Mall (Skelton) / 17.5.1820 meet J Evans / 18.7.1821 meet dr Evans / 25.9.1822 R Evans calls === The first of these entries probably referred to Robert Harding Evans DNB 1778-1857 bookseller of Pall Mall, and Skelton was probably the book Godwin wanted to find or maybe sell (he noted reading Skelton only in 1810 and 1813 and owned one of his books at his death). The last entry, R Evans was quite likely him as well. The painter Richard Evans DNB 1783? - 1871 was probably still in Rome in 1822. Dr Evans could have been John Evans DNB 1767-1827 (see the 1809-10 entries above) or Thomas Evans doctor of medicine of Stockwell Park House, Surrey will PCC 1857
11.5.1824 call on Joshua Evans / 14.5.1824 J Evans calls, from Murray / 9.6.1824 call on Joshua Evans / 16.6.1824 again / 18.6.1824 again / 27.6.1824 Evans calls / 19.7.1824 Evans of Tavistock calls / 28.7.1824 call on Jos. Evans / 29.7.1824 again / 28.9.1824 call on Jno Evans / 20.10.1824 call on J Evans / 22.10.1824 call on J Evans, adv Hone / 7.12.1824 John Evans calls / 26.12.1824 call on John Evans / 27.12.1824 John Evans calls / 2.1.1825 call on John Evans / 5.1.1825 John Evans calls / 6.1.1825 call on Joshua Evans & Jno Evans / 8.1.1825 call on Joshua Evans / 10.1.1825 write to Joshua Evans / 15.1.1825 call John Evans / 8.2.1825 Jno Evans calls / 14.2.1825 again / 20.2.1825 call on John Evans / 22.1.1825 John Evans calls / 23.3.1825 John Evans calls (not in) call on do. / 26.3.1825 Jno Evans calls / 27.3.1825 call on John Evans / 8.4.1825 John Evans call / 17.4.1825 call on John Evans / 7.5.1825 John Evans calls / 25.3.1826 Evans at Basinghall St  / 22.12.1826 again / 8.10.1827 call on John Evans === Joshua Evans 1782-1864  Boase Modern English Biography Supplement was a commissioner of bankruptcy from 1832 when the court of bankruptcy was set up. 2nd son of Hampden Evans (died 1820, possibly the Evans at Rowan's in 1804) of Portrane, Dublin, Trin Coll Dublin, barrister Inner Temple 1816. He was probably all the Joshua  and Jos entries above, all of which were calls by Godwin except the last (write to on 10.1.1825). The first meeting of creditors for Godwin's bankruptcy was on 26.3.1825 so Godwin may have been consulting Evans on whether to declare himself bankrupt. An Evans was present at the two meetings for dividends at Basinghall St in 1826 but he was more likely a creditor. Evans of Tavistock in 1824 was probably William Evans 1772-1847 unitarianhistory.org.uk minister at Tavistock 1794 to 1841, and this was probably a one-off visit. The call on John Evans in 1827 was referred to in Bodleian Abinger c47 f126 Godwin's letter to his daughter Mary Shelley of 9.10.1827 saying he called yesterday, as Mary had suggested, on young Evans who said he had better go to the Jews. Other words in this letter confirm the impression that Godwin had been asking to borrow money. He may have been the same person as the J, Jno & John Evans entries of 1824 and 1825 which continued past Godwin's three creditor meetings at Guildhall though no Evans attended them. The entry of 14.5.1824 Evans calls from Murray echoed the entry of 5.3.1815 Evans calls from Hamilton and this person may have been a publisher's clerk or manager. The J, Jno & John Evans entries of 1824 and 1825 made a pattern of calls only, but both ways. The adv Hone of 22.10.1824 was probably William Hone DNB 1780-1842 which suggests someone in the book trade. There seem to have been three John Evans printers in London between 1815 and 1830. 1) John Evans of 26 Queen St Haymarket 1816-1821, identified in one source with John Evans DNB 1774-1828 but DNB says he only came to London in the year of his death. 2) John Evans of Long Lane Smithfield printer & medicine vendor will PCC 1820 succeeded by Charles Evans will PCC 1828 and John Edward Evans from 1829 to 1839 perhaps will PCC 1835 victualler Strand. 3) John Evans of Budge Row Walbrook 1804 to 1825 in partnership with William Joseph Ruffy 1811 perhaps his successor John Evans wholesale stationer of Budge Row 1839 to 1846 will PCC 1851
17.4.1831 Evans (Euston St) au soir / 27.4.1831 Evans calls / 24.7.1831 Cooke Evans & Osler (Birmingham) call / 30.7.1831 Osler & Evans sup / 22.9.1831 Osler & Evans sup; talk of suicide / 6.10.1831 Geo Evans sups / 16.10.1831 miss Evans sups === This may have been John Evans DNB 1784-1831 again (see 1814 above) he kept a school in Drummond St Euston Sq after he moved to London in his last years, and he died in December 1831. For Osler see Abraham Follett Osler DNB 1808-1903. For Geo Evans consider the soldier and radical MP George de Lacy Evans DNB 1787-1870 but this seems unlikely, also Geo Evans of Peckham will PCC 1833 see above
28.12.1833 A Evans dines / 28.11.1835 again / 29.11.1835 again / 30.11.1835 A Evans (& Emily) call / 31.12.1835 A Evans dines / 20.1.1836 A Evans au soir / 9.3.1836 mrs Brookes (Evans) calls ===

Work notes: 
Emily Matilda Evans born 7.9.1827 bapt 20.8.1828 St James Piccy (buried 1829 there) of George & Amelia, George Evans = 23.11.1826 st Anne Soho Amelia Brough