which drug is best to increase testosterone

There are several synthetic testosterone replacement medicines on the market, but because it is a controlled substance, you MUST have a valid prescription to get them.  A few of the drugs are:  Testim,  Androgel   both in gel form, and injectible also.  There used to be a patch version and a tablet as well, but they are harder to find, if they are even on the market any more.

There is no evidence that herbs, natural suppliments or any "special men's cream" or "tablets" that you see advertised work.  So don't waste your money.  Speak to a doctor if you want to investigate a prescription, but first, get the doctor's assessment on if you NEED it.