Strategy and Tips
The first thing is I think the difficulty on Sahara is a little bit off. I’d probably change Egyptians from Hard to Medium or Easy, Kush from Hard to Very Hard, Berbers from Hard to Medium, and Tichitt from Easy to either Medium or Hard.
The problem with Tichitt is that you don’t have as much easy access to Wealth as your neighbours, and if you end up having to fight both the Berbers and Nok it uses up a lot of food having to cycle armies between them. You do get a decent bit of food so you can build up your cities, but if you mostly sit back defending then Aksum will always win. You need Wealth to be able to punch through someone and keep expanding.
I think when I won on Tutor I pushed to get as much Desert as I could, and took the fight to the Berbers early. I tried to avoid engaging too much with Nok – they might have gotten a few tiles off me, but mostly I’d defend a tile back from the border so I wasn’t threatening their territory, and once they established a border with Kush and Aksum they got tied up fighting there.
So basically, follow the river north, claim as much desert as you can (and possibly the hills north of Nok) and try to take out the Berbers. Power efficiency is the only one that matters for most of the game, so don’t get distracted with the others. If a second / third army will help you break a key stalemate and open things up, I’d probably prioritise that over power efficiency as well.
A couple points on Power – it’s kind of a leaky bucket, where the more you put in the more that drains out. Improving efficiency is huge, especially with the Barracks card, but it can be hard finding the savings for it while actively fighting.
Past the early game, try not to dump all of your Wealth into Power for a single turn unless it’s going to significantly turn the tables – taking a city, or cutting off a chunk of their territory to trap/kill an army. Or, of course, if you’ve just spent wealth on a new army or something else, and you’re covering the shortfall. Ideally, if you can, try to allocate power such that you’re still going to have more wealth next turn than you started with. Or at least be mindful of when you’re dipping into your savings, so it doesn’t end up in a downward spiral.
The other thing is to actively manage it – in the turn when you move to threaten their territory, try and aim for somewhere that they’re not likely to have an army next turn. See how much power they have there, and tune your power so that it’s only a point or two over what you need to threaten it. That saves wealth, and you can dump it back into power on the next turn to hopefully have enough to take it when they come back to defend. You’ll have more power available that way than if you hadn’t lowered it the previous turn, because leaky bucket.
For Tichitt, you’ll want to invest mostly in Desert power technology, as that’ll be where you do most of your fighting. And City power later, but try not to put too much into River / Plains / Grassland just because of Nok. If you take enough desert, you’ll have enough wealth and enough power to come back and roll over Nok later without it (if you haven’t won by then anyway).