Depending upon the strain, dry yeast can be a bit slow to fire up on the first pitch. There's nothing wrong with that, provided it's making nice beer. It's always better on the second pitch, but I think we might be getting ahead of ourselves here.
Can you tell us more about your beer and yeast? Style, brewing method, gravity, and yeast strains will be very helpful--don't worry about being judged, this is a chill place.
Regarding the liquid yeast, nutrient, and O2, that's all good stuff. Are you using O2 from a cylinder, or air pumped through a stone?
Above all else, don't let yourself get too frustrated. There's a learning curve and while it may sometimes not seem like it, you will get over it.