Primal Strike spammer, can be made to basically use only one button
Forcewave spammer warlord/death knight, same as above - on principle i don’t recommend it on a fun basis, but it’s an effective and easy level build
^Blade Arc can be in the similar vein but technically less “easy” because actual melee requirement
i would in general stay clear of any auto attack (righteous Fervor/savagery/Cadence) if the desire is ease of play and power early on, these skills don’t scale as high in the early levels and come with various caveats like less aoe. They become absolutely fine later tho, and have relatively decent low input builds/options with them.
Pets would be another easy one, but they’re not that low button, “lots of pets to summon”, +support skills, they are easy and strong tho (too easy perhaps that some find it boring)
Beam skills are strong but can be a struggle to handle energy management early. Drain Essence and Albrecht’s Aether ray are both options for stuff that has low input builds available.
*Eye of Reckoning can’t be unlocked until like lvl 18-20 similar as with AAR, but it’s also strong even if not a magick beam channel and whirlwind/"spin2win"channelled, if paired with a passive class it can be pretty low button too.
I would not do from Flames of Ignaffar if the goal is low button, simply because Inquis automatically means +2 support buttons for full potential.
Likewise i’d stay away from most demolitionist related stuff if the goal is low input, simply because Thermite Mines etc often means it can quickly become a rotation build with a handful of buttons, specially if maining one of its skills (cocktail/grenado etc)
I’m normally the biggest Nightblade fan, but even if it’s strong it might not be the easiest to play/build, specially if the requirement is low button and as beginner.
Both Ring of Steel and Shadow Strike is fun, but takes a lil going to get the power, so you do sorta rotate a couple skills or use/respec different ones. *RS did make a pretty detailed guide for dual wield ring of steel tho, and iirc someone made a poison Shadow Strike guide too.
RSnoomak, Ralf, Honorabru all writes excellent guides from what i’ve seen