Im still new(ish) to Civ5, but played more then 10 hours
. I can do Emperor, but above is tricky (at best). Not total begginer, but I still remember how it was at start.
The most I learned about Civ5 was when I played as Germans.
Nothing big, no special trick, just a bit better. I mean trick like Koreas "if I have specialist I tech faster then god".
UA: you pay less maintanance for land units. You always get this perk (not like Byzantine and religion). Not big, but helps.
You can also "assimilate" barbarian camps. Helps at start when hammers are rare and you need extra units so Attila doesn't get funky ideas.
UB: a bank that boosts production if you trade with City States. You want gold(bank) anyway and at one point other major civs will hate just because you exist, so CSs will be your only trading partner.
UU: if for whatever reason you have a feeling you can't get SV or CV or DomV is not going so well, Panzer will fix it. In one game I was slowed by Shaka, Persia snowballed. But they couldn't stop my Clausewitz boosted Panzers even when they had (and used) nukes, bombers, rocket artilery, mech infantry and some toys I never seen before that game. I even poped def 151 Persepolis in 2 turns with Panzers only (arties move so slow). Not lost a single one (vs Persepolis, did lost some when nukes where droping).
It's not that Panzer hits so much harder. But because of extra speed (speed kills) I knocked down cities faster then AI could conjure more units. If you do war, do it fast.