You don't need to use HCG at all, and if you do, it's only in the last few weeks of your cycle. You will find many, if not most, experienced people do not use it as the benefit is more or less cosmetic, and comes with downsides. You don't need to substitute anything for it if you don't use it. For those who are on perpetual TRT, it can be useful to use occasionally to restore fertility periodically.