I also recommend giving a 5 needle set a shot. I know I couldn't get the hand of the triangle shape of 3 needles, but the square shape of 4 fixed my problems. It seemed more intimidating, but it was actually easier. The square is closer to the tube shape you are making than a triangle.
I think unless you are a tight knitter, you probably arent pulling tight enough where the joins are. Pulling too tight can cause ladders as well, but the key is at the start of each needle, place the right hand needle very close to the last stitch knitted, and pull tightly enough to take up slack between the stitches, but don't just pull the yarn as hard as you can. It becomes second nature after a while.