Go with a Zenoah G20 or G26. Stone dead reliable, good support if needed. It will make your first gas experence a good one.
If you like to tinker the the 25-30cc homie is a very good idea.
If bang for the buck is important then look at the new MLD 28. Its same weight/size as the SPE 26 but has about 1000 rpm more power on the same prop.