My engine recommendation is going to be based on how much help you have. If you belong to a club with knowledgeable people then you could start out with a 4 stroke, if not I would advise you to go with a 2 stroke. Typically a 2 stroke is just a little bit easier to operate and requires less maintenance.
Sadly the engine selections we have these days IMO is pretty poor compared to what we used to have. There are very few current production glow engines that I would buy. I will do some searching on a few classifieds and eBay and will post links here of engines that I think would serve you well. If nothing else it would give you a good idea of what to look for.
https://www.ebay.com/itm/Webra-40-R-...0AAOSwXh5gMD2x
https://www.ebay.com/itm/Enya-40-RC-...8AAOSw55dgLtze
https://www.ebay.com/itm/HB-Engine-H...IAAOSwQOdf74Ug
https://www.ebay.com/itm/OS-Max-46-S...cAAOSweFlgLboS
A couple of new offerings.
https://www.towerhobbies.com/product.../OSMG0548.html
https://www.towerhobbies.com/product.../OSMG0957.html
https://www.towerhobbies.com/product.../SAIE040A.html