You will hear many opinions on what to get, all must be taken with a pinch of salt since everyone has their own preferences to each other. The only advice I'd give is to go for something of a high quality. Gas weapons are quite tricky to work on for some (I personally find them the easiest weapon to look at but struggle with AEGs lol) but if you buy a higher quality pistol you won't need to do as much maintenance apart from regular/monthly cleaning. Additionally always buy better quality mags and make sure you don't use a gas that's too strong for the weapon system to handle.
Good quality brands include (by aren't limited to) Tokyo Marui, KWA and the newer generation WE products. TM because of the overall quality, KWA for the efficiency of their NS2 systems and WE if you're on a budget. I have/have had TM and KWA weapons and can vouch for their quality, but the WE products I've heard many people talking about wih good results but their early models were notorious for the number of dud guns people received.
...Just don't be yet another glock user, get something more interesting