The Sig Somethin' Extra get recommended a lot.
It's a good kit, I've built two of them myself... Very easy to build and good instructions.

Another Sig kit that's good is the 4*40, it's a very classic plane that many people have built.

Whatever you choose, I'm sure you will get good support from this forum, there's many experienced builders here that'll help you along.
Good luck and have fun building!

ps. Check your budget carefully, building tends to take more money than just for the kit.
You need iron on covering material, glues, hobby knifes and some other basig building supplies such as sandpaper and pins.