Welcome back!
Sader is supposed to be one of the easiest at the higher levels with cheap gears. I personally preferred my knight (I have a sader now, but I also have gears for it

) but that's up to you. I think prison or other glastheim areas are good training with GC, and once you get to a higher level (and/or better gears) you can niff.
Making money is a lot easier than people think, but it does take lots of work (no matter what method you use, other than donating of course). One good place for newbies to start is taking cakes from the Myst Cases in Toy Factory level 2, then selling them to players who will pay 3k or more per cake. I've heard you can make 1m per day this way, though I've never tried it.
(Eventually one of the best ways to make money is to get niff gears for the blacksmith/whitesmith class, but those gears cost around 100m or so total so that's a ways off still)