Forget about belt / beltless ratios, it doesn't matter. Instead, try some different lifts to supplement your main strength work: loaded carries, heavy for short distances; front squat variations, such as no arms (zombie) and partials from pins; strongman lifts if possible, i.e. atlas stones, sandbag lifts and carries, farmer's walk, etc. and also things like Zercher squats (I'm doing these at the moment and they seem to be great for the abs and upper back).
Basically, push your lifts up with belted training, and train for other types of movement (which should help your sport, although you didn't mention what it is) with other exercises. If you have any obvious weakness (abs, lower back, hamstrings, whatever), consider correcting it with some extras, but simply doing a ton of ab pulldowns or something isn't going to help you.
EDIT: I guess your username solves the mystery of what sport you play! XD