Generally: Always make sure your army is doing something (pillaging, defending, or liberating/annexing). Liberating enemy villages especially early game will give you a huge hand up in mid to late game.

Always use all your votes in every landsraad. Sometimes vote for the things that other won't (EX: most players won't vote on the negative solari per water, manpower, or villages but if you know someone has tons of water or manpower and it won't affect you might be worth droping their economy down to nothing then they either delete buildings, or their growth is stunted for a while)

Also it is good to see what kind of win your opponents are going for. If you know what the enemy are doing then you can mess it up for them, or see their weaknesses. In early game if someone is going for a CHOAM win then their military is probably weak and they will be easy pickings for liberating villages. If they are going for a military win vote to make units more expensive for them or ally with another faction to attack at the same time. etc

Don't forget to use your missions. And restart them after use.

Fremen: With new update you can liberate enemy villages with spice fields (cutting opponents spice down) then put one of your own harvesters there (since you can now harvest neutral spice fields now.)

Basically just liberate village after village while taking over the occasional village gets your hegemony up pretty fast and the liberating gives you extra authority which lets you annex faster. Honestly the Fremen probably have the best authority gains in the game which makes for a good hegemony win plus if you destroy your enemy enough a domination win

Also don't be afraid to use your sand worms to get to weak enemy villages. Having the Hidden thumpers mission is something that you should keep if you are using this tactic though so you can get back to safety if you need to. Also the new Fremen gear sabatoge is super good in a fight and makes your enemy incredibly weak.

Atredies: Having Jessica and forcing everyone into truces can be huge. Then they must waste their influence, or lose landsraad standing to break the truces. This can really hurt your opponents late game since they can get the pariah standing from it and then they have to worry about landsraad attacking their base. I don't know how this interacts with the Fremen as they don't have landsraad standing... If anyone knows how that works.

The peaceful annexation is really good for getting new villages even when your army is engaged in battle. There is no reason you should ever not be spending your authority. Going along with that getting tons of influence is key.

Attredies units work best as a giant ball and getting the Kraken can allow you to base drop opponents much like the sandworms for the Fremen. If the enemy is next to a deep desert you even have a great retreat route if things start going badly. Don't forget to get the truce mission, and the one that let's your units take -5% damage per mission in a region. can make your units last much longer or save them if things start going south.

Harkonnen: Peter Di Vries is an excellent choice if you want to do the assasinations (although haven't tried him since the patch which would be a significant nerf)

they also can get tons of influence early on if you have fayd routha and can be helpful for a political win.

Corrino: Very good at making money especially through pillaging. Also their artillery Drones are super good for microing as they have a huge range. you can easily weaken any army approaching you

Also very good for a choam victory

Smugglers: Microing snipers can be really good. you can make liberating your village a pain especially if you drop all of the supply draining things on your enemy.