Cheap Pre and Post-Workout?

Right now I use Surge for PWO, but im trying to reduce costs of everything. What’s good for pre and post workout? I already have a whey isolate/concentrate protein powder with BCAA’s in it, but I need a carb source if im not mistaken. What would be a cheap, good carb source? How much protein and carbs should be taken for pre workout? for post workout?