What do you replace mostly when fixing A/C

[Luis_gz06]

What parts do you guys replace mostly when fixing stock A/C to get it working properly? Ive replaced drier, expansion valve, compressor and recharged it and nothing good yet. The bad part is that im trying to fix it myself. I haven't vacumed it like it should, I just hooked everything up, and put refrigererant. But my main ?? is, what parts have to be replaced most of the time? Thanks!