Play on Easy/Normal level and/or use Soft medieval sub mod to feel ok. Also read Tips and Tricks on mod's main page. This could help also for learing the mod's new mechanics.

Drag all your armies into Constantinople early on; send those that are in Greece and Macedon by sea, choosing "double time" stance once on water - this will be faster than land.

Gather forces near your capital, hire Toxotai, Varangian Guard and decent spearman that takes 2 turns to hire; make sure you have at least 2-3 cavalry besides the general's unit. Voula, you've got yourself a decent fullstack army while doing minimal recruitment and swift transfer from distant provinces - now go and take the Rum city in Asia Minor province.

In the meantime, try diplomacy to delay conflict with Danishmends and Shah-armen, they're likely to take Trapezos from you but who cares - just make sure you keep Sinope to yourself. Also, try trading with Cumans in the north, this will also delay aggro near Crimea. Build a church and remove tax in Cyprus if you don't want to lose it to rebellion early on.

Good luck dude it's a good campaign; try listening to History of Byzantium podcast, episodes 200-220 are exactly about the time this mod resolves, knowing all the nitty-gritty of hRoman hardships at the time makes the campaign really immersive.

Thanks for the help guys,
I've progressed a lot but i'm now stumbling upon a new problem: the food and income drastically change, i have +100 food and +10k income during some periods and then a couple of turns later my troops are starving and I'm bleeding cash. Anyone know how to fix this because I'm in need of more armies which I can't recruit like this because of the risk of destroying my economy/food.

troops could starving from many reasons,not only food. You can "fix it" (income) only by your smart management.

use the software WeMod. Start WeMod, then start the game (Rome II with 1100 AD), then ALT-TAB out of the game to reach the desktop, and then go to WeMod and find the game title using the magnifying glass icon on the upper left. Once you choose the game title, click "Play" and wait until the cheats are enabled. After the "Play" button is greyed out, the cheats are enabled, and now you can choose "Replenish Army", which means your units always goes back to full strength after a battle. However, if during battle you completely lose a unit (its numbers of men goes to zero, or under 5), then you have lost that unit.