I will agree with everyone who says you CAN learn on a Cub, but if you have flown any of the generic high wing, lotsa dihedral, tricycle wheeled trainers, you sort of have to unlearn their characteristics, 'cause the Cub is different from them. I fly a 1/5 scale L-4, built from a Sig J-3 kit. It was harder to learn how to fly it than it needed to be because I had gotten used to flying one of those generics. You MUST learn how to use the rudder, on takeoff, while flying, and on approach and landing. If you have a computer radio, you can cheat and mix rudder with ailerons; using plenty of rudder also helps fight adverse yaw, which Cubs are known for. It helped me, but I usually fly without the mix, now that I'm used to how to use the rudder. I found that the huge wing was a ***** if it was windy, especially when turning crosswind; I'd bank the plane, the wind would get under the wing, or on top of it depending on whether I had been going up-or downwind and it took almost full opposite aileron to level off. But once you know what to expect, it's easy, and you can use rudder and a little opposite aileron and the plane will turn with almost no bank; it really helps in the wind, and also on a crosswind approach to landing.
Whoever in the above posts said something about gradual throttle application is dead on. Rolling the throttle on gives you a little time to input rudder gradually to counter the left turn tendency; the more throttle you use on takeoff, the more rudder you have to use to keep it straight down the runway, and it's real easy to overcorrect and start zig-zagging; when that happens, it's best to back out of the throttle , abort takeoff and try again. A computer radio can help here, too. Program in about 60-70% exponential into the rudder, it will decrease the sensitivity and the tendency to overcorrect. Once you get the feel for how much rudder with how much throttle, start decreasing the amt. of expo; I left in about 30% on mine.
I think takeoffs were harder to learn than landings, at least staying straight was.If you can keep it straight, you got it knocked. After the tail has come up, just nudge the stick back a tiny bit and it will fly right off. Landing a Cub is just lining it up and pulling power back to let it settle, but FLYING it all the way in, and instead of trying to plant the tail when the mains touch down, cut the power completely to idle, stay on the rudder to keep it straight, and let the tail settle; but be READY on elevator to keep the nose from diving, digging the prop in, and ground looping. If you pull back too much on the elevator too soon, the plane will "balloon" and take off again, because dropping the tail increases the angle of attack on the wing, increasing lift. Since your airspeed is dropping, this will be very temporary and the plane will stall, and the plane will drop back to the ground. Grass runways are where this will happen most, because the drag on the wheels will make the nose tend to dive more. I had the good fortune to have both paved and grass runways right next to each other. I prefer pavement, although mistakes tend to leave bigger scars than grass.
I know that this all sounds basic to flying anything, and it is, but it seemed more so to me while i was learning the Cub. But it has made a dedicated taildragger out of me, and has vastly improved my flying skills on everything else I fly. CUBS (and GRASSHOPPERS) FOREVER!!!!