You HAVE to go try them on at a store. Go to EMS or REI, tell someone that you want to get some entry level shoes, and you should be good to go from there.
Get your shoes to fit snug, you don't want any room at all, especially in the heel. Climbing shoes aren't made to be 'comfortable' when you're not climbing.
But like I said again, you have to go try some on. Don't think you can just order them online and be set, I can almost guaranteed you'll be screwed. Like, personally, I don't fit in any shoe but La Sportivas, and it might be the same with you with certain brands.