It sounds like you're very unsure about everything, 'not sure about the dose' 'i'll see what happens from there'
Your plan should be foulproof and you should engrave it in your head so you don't mess anything up. There's no playing around stereoids. - You need to consider all possible side effects, what if fertility is impaired? What cardiovascular changes occur? What happens to blood pressure/lipids/hematocrit? - This is all something that should be researched and learned to be counteracted.
Deciding whether to cruise or cycle, keeping in mind AI dosages... You shouldn't be planning a stack with an ''i'll just see where it goes'' mindset.
Also, GH is insanely expensive at 18.. unless you're rich i wouldn't bother, you'll already get massive enough from gear (unless you're competing..). A simple cycle like test + EQ + primo for 16-18 weeks will leave you satisfied enough as a beginner. It's also insanely cheap depending on sourcing.