Bishop dilemma

Infinity is the best of those 3, it helps while you train cause it saves pots (not everyone is rich and dont care about wasting 300 more pots) and also helps you to resist some high dmg from bosses.

Mana reflection its useless.

Holy shield is only good if you boss a lot.

I wish i could max Bing bang instead of mana reflection... =/

Um, by the time you should/can even up Infinity, 300 pots is about 2 hours worth of pots at Skelegon not to mention 1hitting Bishops still profit just by looting meso. Infinity is a waste of a skill and is definitely the lowest priority skill. The only time you need to tank damage would be for Horntail's tail and level 1 Infinity should suffice because by the time you can up Infinity, your MP should be high enough. Zak's body damage is a joke for bishops.

I don't know how you train and whatever, but as soon as you 1hit Skele you should never incur any losses while training... unless you hold down a Magic Guard -> Heal -> Genesis macro and afk.

Lastly, it's possible to max all skills in 4th job except for a level 16 infinity for a level 200 Bishop. Level 16 is 26 seconds of free MP, compared to a 40 second period. 14 seconds is not a huge loss. Genesis' cast time is 3 seconds? 16,500 MP lost. That's like 1-2 pots only. I guess 300 pots would then be 1000 minutes (16 hours) of training, assuming you remember to use Infinity the moment it finishes cooling.

If you really can not spare a few pots every 10 mins (or spare 300 pots every 16 hours of training), go for Infinity. If not then don't even think about leveling it until the end and don't put points beyond 16.