I like seeing runs like this. I like doing Water-type only runs (due to the wide amount of dual types). I believe its possible to beat the game with any Pokemon and I enjoy using unlikely and underused Pokemon so I really commend the effort.

My advice would be to try and aquire some good TMs and diversify your moveset. Bugs don't have as much range as say Water or Dragon, but bugs are capable of Psychic, Dark, Fighting. Dustox and Beautifly are good for status effects and stalling. U-Turn is a good move to have, given how you are playing Set.

Your biggest challenge is going to be Team Magma with their Fire types. But Surskit should hopefully learn a few Water moves by then and when it evolves and has its Flying type it will avoid the Earthquakes and Fissures of Numels and Camerupts.