Regarding the G meter, unless you have enough aerobatic experience to know exactly what 3G vs. 4G vs. 6G feels like, I would recommend one. You will initially use it to be sure of the amount of G you're pulling and to train your body what this feels like. Once you've gotten a feel for this, you can consistently pull to within a fraction of your target G without looking at the meter. Once you can do this, I would recommend
not looking at the G meter each time you perform a pull. If you are going to do quality aerobatics, your attention needs to be outside as much as possible, and not on the panel.
Aerobatics involves too much variation during a pull throughout a figure, as well as feel for lift/drag subtlety to be relying on the G meter for best performance. Use it to ensure you don't overstress the airplane at first, but then try to do everything by feel. I don't typically look at the G meter until I've taken a break between maneuvers, or have finished a sequence...and this is generally more due to curiosity and confirmation than anything else. My max. positive and negative during a flight are pretty consistent.
In more advanced flying, the G meter can actually be useful in helping judge the quality of rolling maneuvers. For example, if you reset the meter before peforming a straight-and-level roll, you should see exactly +1/-1G after the roll if you did it well. If you see more or less of either positive or negative, you did something wrong. Similarly for rolling turns, if you finish the maneuver with more of either positive or negative G, then you didn't balance your pushing with your pulling, meaning your turn rate was not consistent. You'll need inverted systems for this one.
