it really depends on what enemies youre about to face. swallow is of course the go to potion; when you know youre in for a good fight, yet uncertain to the details.
the journal is really handy in its descriptions of which combinations of potions work well together, according to what types of enemies or situations geralt may find himself in.
true that alot of the potions have negative effects now, but they can be balanced out if one considers the correct combination of concoctions.
a good example would be, say, if geralt were facing several enemies that have powerful attacks, that must be parried, the answer my friends is maribor forest.
now glancing at the journal entry for it, it mentions the negative effects, and other potions that work well to balance out the effects...like swallow & wolf.
check it out! this will help you be even more effective in future battles.
the only knock i have on this is that none of this info is mentioned, under individaul potion descriptions, straight up out of the "meditation" & "drink potion" sections, nor is the above info readily available in arena mode either, when you could really use it.
eventually though, youll memorize some, if not all, of these combinations & youll be a more effective killer for it as well.
not really topic related, but i would also encourage everyone to at least try a playthorugh which focuses on the alchemy branch altogether.
also, if one is so alchemically interested, the most important item in the game (arguably) will be the "mages gloves" that you get right at the beginning of act 1. these allow geralt to harvest more alchamical ingredients than he would otherwise.