yeast question

ok...have been using dry yeast that came in the kits, and now i'm onto liquid with the recipes i see online. i did my 2nd batch this past saturday and just like the 1st batch...i got no bubbling in my air lock. the yeast says to just put it in when its around 70 to 75 degrees...do i always need to make a starter when using liquid yeast? i've never done one, but i know i have links on how to make one...just need your ideas on what i'm messing up

Liquid yeasts have far fewer cells than dried yeast, so a starter is a good idea. Effectively, a starter adds a couple days to the growth phase.