It's the same for me, when I come out of the pump I'm semi-hard and usually somewhat discolored...purple, camouflage-type markings that go away when I do my manual exercises. But when you get expansion, you'll start to notice that when you stimulate yourself back to a full erection you can feel the chambers in your dick are wider and harder than before...that's how it functions as an "erection enhancer," at least for me.
I didn't really see any expansion my first few times pumping either, but there are a lot of variables to consider with that...which
gaiter are you using? How long are you staying in the pump? How many sets? Is there any air in the chamber (ideally not)? Are you doing manual exercises, and if so, which ones?
There's a bit of a learning curve with the pump, but not a big one. Feel free to check out
my thread on the
Penomet for some ideas as you experiement.