I would recommend him to try what looks fun. You recommended the three strongest ascendancies in the game, which is fine, but also it’s kind of a cliche and boring suggestion to me. No offense. There’s so much more to the game than just playing the builds with the highest damage numbers.
If your friend just wants a strong build and doesn’t actually care what the playstyle is, then your three suggestions are great. But if your friend has any actual idea of what they want to do, then tell them to lean in to it. There’s builds on mobalytics for just about any skill. Do they want to play melee? Caster? Ranger? Ice build? Fire? Chaos? Lightning? Physical?
Personally I can’t stand builds like CoC comet because there’s too much screen clutter, but maybe your friend loves the screen clutter. There’s just not really enough information for the community to recommend a good build for your friend.
If you’re just generally looking for random build recommendations, then my top three favorite builds in the game would be Ice Strike monk, Sparks sorceress, and ED/Contagion witch.