First order of business should be the fire opal hitpoint rings. It truly is the best bang for your buck. No other items prior to the Planes (or maybe some obscure long ass high level quest) will net you 90-110 extra hit points in classic.

I think this is an excellent option TBH. Both this and the ghoulbane are good choices and both will run you in the 500p range (a bit higher for both TBH, but if you shop you can find them for 500-600). Just whatever you do don't spend it all on a bunch of random junk he'll outgrow in a couple of weeks anyway. Better to spend it on a few pieces he'll use for a long time. Not only that but the resale value on junk is pretty bad whereas if he ever gets bored of his pally and you're trying to sell the ghoulbane again you'll probably find a seller fast and you might even make some profit on it.