Not to bust your balls....well maybe a little, but if you are starting a cycle and don't know this then it would be my advice to do a bit more reseach. "roids" are not magic and can be very dangerous if not done properly. How about some stats, cycle plan, pct plan.
Someone has to tell you this bro. Use this site to learn from the mistakes that others have made. Trust me there are a lot you can make.
23g 1" or 1.5" is fine for most gear. Some oils may be a bit slow going in, but there's no rush anyway.
The length of the needle is okay, but I have never personally seen a 1.25" pin. The depth of the injection will be based on how much muscle you have at the injection site and the injection site itself. 1.5" in probably too deep for most guys for delt injects, so don't push the pin in all the way. Oh yeah and be sure to keep everything sterile and always use a new pin. Don't draw your gear and then shoot it with the same pin either.
Please do more research and ask more questions. I would hate for anyone to get hurt using gear the wrong way.