You are going about this the right way by asking our community for their advice in regards to which ‘first’ AEG you should buy. Funds aside, (circa £550), any AR/HK TM out of the box is superb. You will not be disappointed. The 416 Devgru is a great looking gun too and it has a good weight to it albeit a tad front heavy do to its rail. The only thing you really need to do to it is the deans connector mod. Ask the retailer to do that for you. And then of course you will need a few more magazines. Don’t bother with hicaps as the the bolt stop will not work with that type.
And here’s a thing, if you have not used a TM recoil before ask someone at your local site if you can have a go on theirs. 99% of the time peeps will be happy to show you what they have.
And one more thing as Edcase has said above, get proper boots and proper eye pro.
Ah one more thing too. Don’t go cheap on a decent sling, if you think you need one that is. The last thing you want is a sling from failing and your shiny new pew pew hitting a concrete floor.