I'll be using it for gaming and the Internet, basically. I've been looking at several Asus monitors. Should I go for an IPS monitor given the money I'm willing to spend?
I don't think you'll find a new IPS monitor for that price - a TN panel is probably what you'll have to get.
Here's an excellent deal for a 24" 1920x1080 monitor from Walmart. You probably won't find another new one of that size for $129 anywhere. AOC is a good brand - just not as popular as ASUS. Over 200 reviews and 94% said they'd recommend it to a friend.