im no expert, but ive found that if u learn a few base combos, it'll help lenghthen ur combos.
atw-atw-co-htw is a very common one and u only use 1 leg.
try to do that then the same thing after it so atw-atw-co-htw-atw-atw-co-htw.
also learn something like atw-hatw-atw-atw-htw-htw-atw-atw-co-htw. hatw-atw-htw-hatw-atw-atw-co-htw. learn those, they should help u lengthen ur combos.