If you're drinking coffee for purely instrumental value, don't buy it from coffee shops. Also don't drink espresso, as it takes longer to make and/or is more expensive. The instrumentally ideal coffee is black, the cheapest stuff you can choke down, and preferably made by someone else (who you aren't paying to do so).

That said, I drink coffee more for pleasure than productivity. I can't say I really endorse it for such purposes--caffeine tolerance builds up too quickly for it to be sustainable, and the negative productivity while decreasing intake seems to more than outweigh the gains felt while increasing.

I suggest acquiring enough of a taste for coffee to not hate consuming it, possibly by drinking decaf, but don't drink it regularly otherwise--reserve it for an occasional (weekly or less) shot of safe, legal stimulant when it will do the most good.