The player who call often is a non beleiver. You need to put lot of chips if you want bluffing against him. He dont beleive you hit the straight or the flush. Dont bluff in this situation and if you hit hard punish him lolll
If you are playing low stakes, don't bother trying to bluff. Play nit poker and take them to value town. You can start bluffing against level 2 thinkers.