Question

I am trying to build my Bulbasaur to level 100. What are the best moves for it?

Answer 1

You'd be better off evolving to Venusaur obviously. But if you really want bulbasaur, the same movesets still apply, see here:
http://pokemondb.net/pokebase/7692/good-moveset-for-venusaur
http://pokemondb.net/pokebase/3111/what-is-a-good-moveset-for-venusaur

Answer 2

Bulbasaur
Item: Eviolite
EVs:252 Def/252 Sp Def
Ability:Chlorophyll
Timid Nature(+Spd,-Atk)

• Sunny Day
• Solar Beam
• Sleep Powder/Toxic
• Giga Drain/Venoshock

Sunny day doubles speed and provides no charge for solar beam which is a really good combo,
If you choose Sleep powder,then it should be with giga Drain for venoshock would not do much damage.
If you Choose Toxic,venoshock will have double power,how ever you can also choose toxic with giga drain for better recovery since bulbasaur doesnt have a decent hp stat.
But you can also evolve bulbasaur for better stats.

Answer 3

Here are some Bulbasaur/Venusaur moves that are good. Make sure to evolve Bulbasaur by at least level 98 otherwise you won't be evolving it.

Sp Attack moves:

Solarbeam, Leaf Storm, Petal Dance, Grass Knot, Energy Ball, Sludge Bomb, Hyper Beam (if you like those kind of moves, but want a more reliable Grass attack than Frenzy Plant)

Attack moves:

Double-Edge, Earthquake, Return, Facade, Knock Off, Outrage, Seed Bomb, Power Whip

Stat moves:

AMnesia, Ingrain, Curse, Grasswhistle, Charm, Safeguard, Light Screen, Block, Worry Seed, Synthesis, Substitute, Rest, Sleep Talk, Sunny Day, Swords Dance, Protect, Toxic, Roar, Sleep Powder.

For more concrete movesets, go to the links given by Pokemaster.