With Leaf Stone Gloom evolve to Vileplume and with Sun Stoneit evolves to a Bellossom.
First now lets see the Pros and Cons of both
-Solid SpA stat
-Good HP,Def,SpD stats
-Movepool isnt wide for coverage
-Solid Spd,Def stat
-Atk and SpA Somewhat good.
-Learns Solar Beam as a level up move
-Low Speed as Vileplume
-Again not many coverage moves.
So almost both are same in Speed and Movepool but Vileplume Seems to be better with great SpA statas offense is important in games.But Vileplume has weakness against Psychic that is against the the Sevent Gym.
-Solar Beam/Petal Dance
-Giga Drain/Sleep Powder
Sunny Day to activate Chlorophyll and increases Speed.
Sludge Bomb and Solar Beam/Petal Dance for STAB and Higher damage.
Giga Drain for life recovery.
Sleep Powder puts the opponent to sleep and allows you to attack freely.
So evolve it to a Vileplume using a Leaf Stone Staright away
Hope I Helped