This is an area of personal expertise for me. Most people have no idea how to buy jewelry.
Feel free to private message me with any questions.
My top tips:
1) Find out what your girlfriend wants (search her Pinterest, talk to her sister/mom/best friend, or talk to her directly and involve her in the shopping). She may want something antique, something modest, something non-diamond. The only way to find out is by communicating. The proposal can still be a surprise, even if the ring isn't.
2) Set a reasonable budget based on reality. Don't go into debt for a ring. Keep in mind some places offer upgrade policies, so you can buy something smaller and very nice now, then upgrade for an anniversary.
3) Learn what you can about diamonds online. Cut
is what makes a stone beautiful, not clarity, color, or even size. A well cut smaller stone will outshine a poorly cut stone any day of the week! Pricescope.com is a wonderful site with many experts/prosumers who want to help. Join us over there in the forum!
4) Don't buy from a chain/mall jeweler.
5) Buy online from a reputable jeweler that shows pictures of the actual diamond you are buying and setting, like www.JamesAllen.com
, etc. If not into diamonds, let me know and I can suggest other sites. A friend of mine got a lovely pearl ring for his now-wife. It's not very wearable for every day, but she got a nice wedding band she wears instead.
Again, feel free to message me with any questions.