Before you just cut power to the suspension compressor, you need to bring your car to a good mechanic and have them find out whats leaking air and causing your compressor to keep running. If you just cut the power, after your car sits for several hours the air will drain from the system and your car will be sitting so close to the ground you will not be able to drive it. At that point you can add the cost of a towtruck to your repair cost!
Well runite is the most expensive - around 19k per ore. But a better thing to do is just make bars of whatever ore you can mine/smith. Even if you buy the ores and make them into bars they sell really well.
Pull the relay, should be located under the hood, but be prepaired to reinstall it, some cars need to be hooked up to the air supply or the air will slowly purge out of the system. Maybe take it to a garage and have the problem diagnosed as why the system is staying on, maybe bad wiring or maybe a leak in an air line. Fixing the problem is better then band-aid repair jobs. I did the same thing to my truck when the ABS started acting up on it, I know the problem, but its not worth fixing, pulled the relay, and the ABS system is deactivated. Same will work on air suspention.
Had the same happen to my GM car. There are several things that can cause the compressor to keep running. A leaking o ring going from the air supply lines to the shocks and relays. A faulty leveling switch on the axle. My car came equipped with a switch in the trunk that you could press a button to inflate tires and inner tubes etc. If you have this switch in the trunk try to turn it to the off position. If this was turned on the compressor will run on bypass mode instead of raising the shocks up. I put my car in the garage and actually heard the air leaking out of one of the lines running to the shock and was able to fix it.
I'd say iron or coal. Of course rune costs a lot but it respawns every 15-20 minutes. Iron and coal costs 250 each same with gold, but iron is the fastest (and the best exp). I recommend iron until your a really high level.
