What's missing?

[Wya77]

This is my first playthrough of a Johto game, so I'm not real good with the Pokemon.

Definite Pokemon
Quilava lv. 18 @ Charcoal
- Quick Attack
- Headbutt
- Smoke Screen
- Ember

Zubat lv. 17
- Leech Life
- Astonish
- Supersonic
- Bite

Heracross lv. 19
- Brick Break
- Horn Attack
- Endure
- Aerial Ace

I need a grass and water type for sure. I'm going to use Chinchou when I get the chance to get it. I'm not sure about the grass type.

Are there any other spots that I need to cover that haven't been covered already?

 

[Calamity]

Your first 3 pokemon look pretty good so far considering you say you're new to the pokemon. A grass type isn't really needed, they are pretty lackluster as you progress through the game. I would of reccomended a Mareep but Chinchou covers electric type. So if you are dead set on having a grass 'mon I'd have to say Exeggutor is one of the best ingame, can deal huge damage with two good STAB moves Solar Beam and Psychic. With huge special attack and a speed boost through Chlorophyll / Sunny Day, Exeggutor is definitely a good choice. :)

 

[deoxys121]

Since you have the "basic types" (as I call them) covered (my basic types are Water, Fire, Grass, Electric, and Flying), you can now fill in your sixth slot with an extra type. What ShinySalamence said is a definite YES for a Grass-type, and you cover Psychic there too. Now, for your remaining slot, maybe you could try a Rock or Steel-type for a bit of a wall. Sudowoodo, with 100 base Attack and 115 base Defense is great both defensively and offensively. Also, make sure your Sudowoodo has Rock Head, then teach it Wood Hammer via the move relearner in Blackhtorn City. So, a great moveset would be Stone Edge, Earthquake, Wood Hammer, and either Hammer Arm or one of the elemental punches taught from the Battle Frontier.