a little too lake now, but I don't think you'll ever use up that ph up. I bought a gallon of each up and down, and I've ever only used about 10 drops of ph up. You'll probably only use the ph down, as bubbles/ oxyen makes the ph go up. The more oxygen the more it goes up. But that's not a bad thing. The more bubbles the happier the plants.
As for the solutions, the two differet ph solutions are used to calibrate the meter to two values. You can just use one, but the two stage calibration makes it more accurate. I could explain, but it would be boring and take a lot of typing. Not sure, but I think the probe solution is something to keep your probe in when it's not in the water. It should always stay wet. Letting it dry out will mess it up, and you shouldn't just let it sit in water when it's not in your tank. Does that make sense? SOme might say it would be a waste of money for that stuff, but I think it's cheaper than getting a new probe.
Hope that helps bru. Cant wait to see what happens.
peace