Persia is very not newbie friendly because it takes a lot of knowledge and finesse to make the most out of their UA. I'd agree with some others here who recommended China. First of all, if you want to go for a domination victory than Great Generals will be of great use to you, they're always useful but especially for domination. So if you don't like using them now, better get used to start using them if you want to be serious at domination games. Secondly, unlike other civilizations who have UUs that you use instead of the standard army composition, China's UU is the main part of the standard composition, just an improved version of it. Since you've won by all the other methods than I must assume you're familiar with the CB rush and than its natural followup into Crossbows and Gatling Guns. China simply makes this very standard army tremendously stronger, both due to the Chu-Ko-Nu as well as their Great General bonus, which allows you to field multiple armies and have a Great General for each, and even some to spare for defensive citadels. Going for domination, especially on Immortal/Deity will force you into multiple front wars since the AI loves to DoW warmongers, and going for domination you will be a warmonger and will piss off a lot of AI civs. Therefore you will need to be able to fight on 2 fronts on a regular basis, and occasionally more than that. You'll want to do this regardless of AI DoWs by the way, since it speeds up the process and teaches you how to make the most out of your troops, which is another skill you need to master as a domination player. All in all, China makes for the best beginner nation to domination victories as it's both easy enough thanks to the UA and UU and because it doesn't force you out of the standard composition like Arabia, Mongols and Huns who were also mentioned here. You always want to start with the standard, before moving onto different variations.