With omaha H/L split, you want to be playing card combinations that give you the nut low draw, plus ways to make a high hand.
Good low combinations include: A2, A3, 23
Other low combinations that don't play for high extremely well are pretty unplayable. So the only hand without those low combinations that I would play would be like 3456 double suited. But even then, that's pretty speculative.
You can also play high only hands in late position. Stuff like QQJJ, KQJT, ect. are playable in late position with either a very large multiway pot (worth winning only half) or in an unopened pot (since you can raise, and often steal the blinds).
But that's all advice for limit omaha 8. Pot limit, I have no idea, but generally you want to be even more focused on playing to scoop since the bets are larger & the pots are less multi-way.