The steam version is best but if money is an issue you can download the free version and get tile sets so it’s not acii.

Whatever you do, be sure to check out DFhack. Helps to automate somethings and give you more control.

Try to focus on one thing to learn per fortress, and just build random other stuff to check out. Once you know the basics then you can start fortresses with big projects in mind.

You don’t have to make a new world to start a new fortress. You don’t have to wait for all the dwarves to die to abandon the fortress. Retire the fort you got going and start new somewhere else in the same world. If you get sick of fortress mode you can do adventure and you can go on adventures to your old forts if you want. That’s why I keep remaking in the same world at least.

Plenty of video guides online. Nookrium and Blind are the biggest contributors I think.