I got a 3 bag set, am going to buy more.. I wouldn't get anything smaller than the 5 gallon bags, and mine are all-mesh so they drain faster.. Also if any wear out, lots of extra mesh to sew a new one from an old one. My 3-bag set was 20, 70, and 200 micron. I will be ordering the 110 and the 160. Those five bags and you'll be set. The 160 collects the garbage that washes out of the 200.. you probably don't want to smoke the 160. You need the 70 and 110 because without those, the 20 will be so full it will take too long to drain. I mix my end products together for consistency.