Right now, I am feeling bitter, jaded and cynical enough to say, don't give out any treasure whatsoever. It just seems kind of pointless to me. Apart from upgrading armor, there really isn't much to spend gold on, and the game assumes that the PCs don't have any magical items, anyway.
Hmm. I think the game assumption is more that the PCs don't
need magic items, not that they don't have any.
In lieu of any guidelines, you could do what I do in my 5e campaign: work out what is the minimum treasure I can get away with giving out, then halve it*. I can always give the PCs more treasure later, but I can't easily take it away if I give them too much.
*I'm not entirely serious here, but it never hurts to keep the treasure low. At low levels, just give them enough to make a living (base it on the living expenses section in the PHB - and I don't suggest making anything above "comfortable" viable for many levels).
Yes, good point. In other words, don't "spoil" your players.
I'll say the reverse: treasure is fun. Give out more than you think you should, especially at low levels when there's plenty of time to adjust later, and then watch to see how they use it creatively.
Yes, treasure is fun, but there's such a thing as "too much of a good thing." I've learned the hard way that too much treasure--especially too many magic items--ends up working against the Tresure Is Fun Principle (TIFP), and can even lead to jadedness and ennui ("Oh, no another
vorpal weapon, how gauche...throw it in the
Satchel of Infinite Holding with my
Sword of Kas and
Staff of the Archmagi").
To the OP, while I imagine there will be guidelines in the DMG, for the time being I think it really depends upon what sort of game you want to run. High or low magic? Quick or slow advancement? Magic items scattered about in every nook and cranny or a rare find? You have to find your own balance. But again, I think the "less is more" principle is good to keep in mind. Fewer magic items makes them more special. But if you make them few and far between, you can spruce them up - give them lore, maybe even secondary powers. A
+2 mace is rather boring, but the permanently blood-blackened weapon of the infamous Grand Inquisitor Karthul, which creates a moaning sound that causes all opponents to make a saving throw or be smitten by fear, adds some flavor to the mix.