Don't remember about the airspeed off hand.
Compasses: Think of a card mounted flat on the dash. The card always points north. Well, you're reading the back end of the card. If you turn left, the card turns clockwise. The text appears to move from the right to the left since you're reading the back of the card.
The reason the compasses on the dash (btw, they all turn that way) turn "backwards" is because you are reading the actual compass, but from the back.
The directional gyro, which is vertical mounted is a completely different item.
The turn coordinator has no relation to an attitude indicator. The bank required for a given rate or turn changes with airspeed (higher airspeed means higher bank). The line on a turn coordinator always means 180 degrees in a minute (2 minutes for a circle) and thus doesn't have a bearing on what your actual angle of bank is. You can do without one or the other (turn coordinator or artificial horizon) but you really need at least one. You can uise a turn coordator to maintain control if you don't have an artificial horizon.
VORs are fairly important. Having dual VORs allows you to identify fixes defined by two intersecting radials from different VORs. DME also helps. Distance Measuring Equipment tells you your slant range (true) distance from a VOR and some fixes are defined that way. We use GPS in our aircraft *usually* to define VORs and fixes, but VORs are still very useful.