Well, many things but depend on the person....
First, Dueling, If you see that you are really pro at a skilled mod then start dueling, if u aren't don't duel or u will waste ur tc.
Second, Marketing, its like how danwebb said, if you just know how you will do it, and if you have marketing skills, then go now.
Third, i think its easy to buy items? i can give u some nice items u should buy with the 30k and it will not be a wasted, but buy it from the Forum not market/shop.
512 Head texture, its like 18k because there are non in market
and force+relax from these colors
Amber
Acid
Hunter
Raptor
Noxious
Persian
Tyrian
Helios
Titan
olive
vampire
camo
beetle
All these colors match your qi and its not more than 10k