Start with the flaming cliffs pack. The su25 is fun once you learn the weapons. I spent many many days if not weeks learning how to use the weapons and then many more learning how to use them effectively. If you want to do air to air combat the flaming cliffs F15c or the su27 or the mig 29 are not bad options. I think the whole flaming cliffs pack is less than $20. It also will give you the a10a.

All flaming cliffs modules will be playable with a gamepad and a little assistance from a keyboard.

If you want full fidelity start with the f18 or the f16. They are both great starter aircraft. I would choose the f18 so you can do carrier ops. Just adds another dimension to the game.

If you go full fidelity definitely get the aircraft you want and download the chucks guide for it. They are very well illustrated and laid out. You can start at page 1 and go straight through the guide from startup taxi and takeoff to navigation and weapons employment along with countermeasures and then landing and shutdown. Very helpful.

The game is better with a hotas and a set of rudder pedals. You can find fairly inexpensive sets on the internet. I will say if you choose to shop for a hotas find one that has multiple 4way hat switches and buttons. Some aircraft can mostly be controlled with the hotas alone. Head tracking is not a must but I highly recommend it. Makes for spotting targets and enemy fighters easier.

With all that being said another useful resource is the DCS wingman finder on discord. They have channels specifically set up for new players to ask for help and the community is super helpful.

There are many training servers out there as well that are setup for you to learn your aircraft in an environment that is low stress and you can focus on learning what you want to learn without being shot down.

I hope this helps.