22 stitches per inch is usually considered DK weight or light worsted which often has a the number "3" on the label or listed with it on websites.
I would think any kind of yarn with that gauge should be fine. Kind of depends on what you want. If it's a summer sweater you might want to stick to cotton or cotton blend. A lot of websites let you search just a specific weight which is handy. Some you have to look for the term DK or light usually.
Not sure of your budget, but here's a few sites that you can look through to see if they have what you're looking for.