Things with buy limits are great to alch like d'hide bodies, battlestaves and rune items. If you just wanna go bulk then look into some different bracelet prices and longbows.
D'hide bodies is always a good go to if you're looking to buy.
Personally, I would always choose Super Heat if you're looking for mage lvls though.
Smithing + mage = the deal.
before i hit 99 mage i used to alch different battle staves and d'hide bodies. One of the ways i got around the GE limit was using about 4 different accounts. which even then didn't allow me to buy as many as i would have liked
Id Go with the d'hide bodies or If you want the classic try Yew Longbows. , I'm not sure if i'm allowed to post the link but u can google it and there's a site with exact profit margins/ and losses etc.