I've raised a Bellsprout before, I would suggest waiting until it learns Razor Leaf at level 39 before you evolve it as Victreebel doesn't learn any more moves until it learns Leaf Storm at Level 47, you could evolve it before level 39 if you have a decent grass type tm you can teach it (e.g Solar beam, Grass Knot etc)
Progress Update:
I haven't made alot of progress since yesterday as I found the Game Corner and have been addicted to the Voltorb Flip game, I also won the stamina event at the Pokeathlon with my Steelix, I lost the Speed event there though, I battled all of the trainers in the underground and eventually made my way to Ectruteak City.
When I arrived in Ecruteak city I spoke to Bill at the Pokemon Centre and healed my pokemon, after that I headed to the Kimono Girl's place and battled the Rocket Grunt there, I went to the burned tower after that where I spoke to Eusine and Morty, I battled the rival and headed down to the basement where I encountered the three legendary dogs, I spoke to Eusine again and finally left the tower.
I headed to the gym and battled all of the trainers in there, I lost to Morty (unsurprising considering I didn't heal beforehand), I'm going to train my team to level 27 tomorrow and try again.
My Team;
Quilava Lv24
Sunflora Lv23
Misdreavus Lv24
Steelix Lv23
