Whatever chisels you get, learn how to sharpen them. Maybe even get a cheap set to practice sharpening with. A bench grinder is handy and can speed things up, but can also wreck things, so best to go easy. There’s a lot of debate about water stones, oil stones, diamond stones, and some thick glass and various grades of decent sandpaper (you’ll need the right sort of paper though; google scary sharp for more info). I like a Japanese waterstone but you have to make sure it’s perfectly flat otherwise you’ll end up with a curved edge on your blade. You can true it up with that same piece of thick glass and sandpaper easily enough though. Some people might like using a roller guide to assist sharpening, but don’t use one of these with a stone, as you’ll just ruin the stone. With practice, you’ll be able to sharpen up any blade by hand, to a more than acceptable level.
I’ve actually been using some cheap Silverline chisels to reasonable effect, but the stuff I do hasn’t needed really good chisels really. Thinking of upgrading to a better quality set for more complex future projects though. I’m told Ashley Isles are good value, but have no experience of them really. The Veritas ones look really nice, but are very expensive. Mind you, a friend is thinking about a set of Lee Neilson chisels; they are definitely not cheap!