Why did you have to restart(again............)? But in all seriousness, yeah, Adamant is the best nature for Chespin.
Anyways these are the starters you can receive later in the game; Bulbasaur, Cyndaqui, Mudkip, Piplup, Tepig, and Chespin. So you CAN choose them, I'm not saying you can. I'm just saying these are the starters you can get later in game. If you really want a good companion, then I would suggest getting a Torchic, Chimchar, Snivy, Charmander, Treecko, Turtwig, or Froakie. Those are the pokemon that helped me the most when I was deciding what starter to choose.
Reasons for the starters I chose;
Torchic: Speed Boost(must I say more? well okay! You can get 2 Heart Scales early on, and you can give those two to your Blaziken. Letting your blaziken learn HJK and Flare Blitz early game).
Chimchar: Iron Fist and it's moveset is amazing~
Snivy: Grass type, Contrary for it's ability. It'll be great early on against Julia and Flobot's Cradily. It also has a decent moveset as well!
Charmander: Dragon Rage....Dragon Rage is soooooo OP early game. Of course you can also get a Gyarados to learn Dragon Rage.
Treecko: Because of it's moveset
Turtwig: It's typing in Torterra is so good. It also get learn a ton of cool moves as well like Wood Hammer, and EQ(Earthquake).
Froakie: Protean. just.....Protean