Sorry in advance for such an unhelpful post, but...... whatever fits you best. Go to a store like Mountain Designs, or Mountain Equipment, and get the people to help you. It should fit snugly around the toes, sides, and heels, without hurting.
If the shop is good they usually have a bouldering wall for you to try out the shoe on!
Reputable brands include Scarpa, FiveTen, La Sportiva, Mad Rock etc.
Definitely take your time when choosing a shoe. And sizes vary hugely between brands so always try 1 size up /down if you are not sure. One time I saw a pair of shoes for the bargain price of $50 and it was the same size as my old pair of shoes (although different brands) so I quickly bought them. Turns out that they were way too big, and I could put a finger between my heel and the shoe at the back (how did I ever miss that?!?!) So just be aware that sizing is quite different between brands.
For a beginner, you want the overall feel to be comfortably snug but not painful at all, with the toes curled up ever so slightly. Really hard core people go for the very painful squeezy shoes, but that's not me, so I can't really say anything about it!