Assorted picking thoughts
Alright, we're first pick. It's a great place for winning, less good for trying janky synergy picks. Generally the strategy here is to prioritise brute-force power, and ignore synergy. My understanding is that usually you want a leader first, as your traits make more difference than your civ. Having two traits that synergise with each other is great (e.g. IMP/ORG), we just can't rely on synergising those traits with a specific civ (e.g. EXP/Khmer or Ottomans). Our civ will probably end up being 'best remaining civ of x techs,' unless we luck into something cooler.
I would consider:
Organised: is one of the strongest traits in CtH, and also one of the easiest to use effectively. Running a civic? You're making money. Building cities? They'll probably want courthouses. You get the idea. Assuming you'll want a courthouse in every city (Emperor difficulty), and a lighthouse in some, that's 60-90 hammers saved
per city. Because your tiles aren't buffed, whipping hurts less than with FIN. Because your expenses are lower, you can skip gold buildings for more science buildings and units. Your base espionage ends up way higher than other players'. It's always useful.
Imperialistic: More settlers = good. IMP is weakened by Emperor difficulty somewhat, since you can crash economy more easily (see: IMP players in PB60). I like it the least of the three expansion traits, but it's the consensus strongest and has good results.
Expansive: I like this better than IMP. It's more flexible (granaries are good even when you're bankrupt), and it's much easier to overflow into a granary than a settler anyway. Also lets you chop granaries at size 1 in new cities, which is a bigger deal than whipping settlers 1-2 turns quicker imo.
Creative: If PB60 was anything to go by, Tarkeel tries to make creative relevant through mapmaking (though that's a dangerous assumption). It just makes the first 100 turns so much easier, and it's amazing for border struggles. FWIW, I also think Creative synergises with Serfdom civic, because it allows cities to be settled further apart. That could actually be relevant, because I would expect Tarkeel to consider the Serfdom/Slavery dynamic (that is very meta-gamey, though).
Financial: I prefer Organised, but it's hard to argue with free commerce. Definitely better in the lategame (e.g. PB59), but takes ages to get there.
Protective: I think this is better than Financial on small maps, and worse on big ones. Specifically player count is relevant, because with enough OB Protective sucks (e.g. PB59). It's also much better with islands. Not sure how that will factor into this map, so the trait is somewhat risky.
I am neutral on:
Charismatic: Cheaper border pops are decent, but the happiness is not often relevant without WW. Plus RB maps tend to have a lot of luxuries. CHA is a victim of our meta, sadly.
Industrious: My personal favourite trait. Stronger in smaller games, or at the end of a snake pick where you can guarantee that few other players took it. But I do think IND is under-rated, and I'd be very happy to go for some wonder shenanigans if you are.
I would not recommend:
Aggressive: I still don't think this does enough. I would rather focus on getting the foodhammers and/or commerce you need to create a strong army, rather than a few free promotions. The trait is less 'bad' than it used to be, but I don't think it's 'good' yet.
Philosophical/Spiritual: I'm grouping these together, because they have the same issue. You can do great things with them, but they often rely on synergy (you want something to go for, especially with PHI bulbs) and they're very difficult to play effectively. But I definitely want to try them, especially SPI, so I won't stop you if you to be a guinea pig.
Overall, it's hard to go wrong with a leader that is 'expansion trait'/'economy trait.' It's a very safe combo to reach the midgame, where you can try economy or warfare depending on what you're feeling. So things like IMP/ORG, EXP/ORG, EXP/FIN, IMP/PRO, CRE/PRO, and so on. With that said, I think double economy, or double expansion traits, are also very valid.
Of course, if you have your heart set on anything, I think you should pick that. That includes janky synergy picks, or going civ-first. This is just some general thoughts if you're looking for ideas.