"experience" limit? Do you mean expertise? There are incense you can buy on the item store that increase both your experience and your expertise gain by as much as x5. But just between you and me, those things are not worth buying from the item store. AP has a macca equivalent, in general you can sell 100 AP for 100k macca easily. Most of the items from the item store are actually a rip off in terms of AP price, you can get them cheaper for macca.
Your best bet is to either sell AP to someone in the game, (you do that by buying stuff for them, and they pay you the equivalent price in macce) The best item in terms of macca worth in the item store, as far as I can tell, is 10 Link Melons. You can get 10 for 1000 AP, and sell them for 100k each pretty easily, that gets you 1 million macca. I don't think there's anything in the item store with that good a conversion rate that is as easy to sell. You can then turn around and use the macca you got to buy stuff like incense at a much cheaper price than you would at the item store.
Right now 5x expertise incense is really cheap for some reason, I'm not sure why, but you can buy it for 150k each. Best way is to go to Babel and listen for people's shouts. Also, the best way to sell stuff is to go to Babel, channel 1, and shout. You can also use the bazaars, but it's a waste of money if you don't have 5 things to sell. Also the bazaar tax is pretty large, so it's better not to use them on big money items. When I'm trying to sell Link Melons, I usually go to channel 1 and repeat this shout: "S> Link Melons 100k" every 5 minutes or so. I can draw or do whatever while I'm doing this so it's pretty easy.
About poker heroes... yeah, when I first started playing I thought the same thing as you. It seemed like pocket A's and K's were coming up too frequentally. But after playing there for awhile, I think I was mistaken, it seems pretty normal. It was probably just luck that that happened. Everyone calls on most hands, and nobody ever seems to fold draws, so you're going to see more big hands in general.
Yeah, the virtual room with the slimes is where most people build expertise. It's great for building all kinds of stuff. Hey, if you're building up a melee character, make sure you don't ignore spin attack.