250 is good for first cycle, i started with 200 and it did some job, although i'm going to titrate up for a longer time and not call it a x weeks cycle. Considering i was already a natty gymrat for 19 years with a good amount of muscle and my natural test was 650 before i got to gear, i think anyone should see and feel a difference with 250 as a start. You could actually be at 250 for lets say 12-16 weeks and then bump the dose to 350-375 for another 6-8 weeks and your bloodwork will probably take less beating than doing a 12-16 weeks at 500.
What's your bodyfat? It plays a role on your AI dosing, although i suggest bloodwork after 4 weeks on cycle to check your tt, ft and e2 at least. 2 shots per week it's easier but you won't be as stable as possible, and you need this especially on your first cycle because you don't know how you will react to sides like acne, water retention, blood pressure etc. IMO do at least 3 shots per week. With a simple estimation for 250 test divided in 2-3 shots per week you may need a full tab aromasin or arimidex splitted in your shot days. If you add HCG you'l probably need more. If you're lean enough, under 10% bodyfat you might need less AI.. Only bloodwork will determine. Don't trust your feelings because i overdid it with HCG and my e2 came at 106..and i didn't experience ANY side effect.