Just wait, eat, lift and learn. Back when I first started running gear I spent a full 2 years fan-boying over anything bodybuilding related, articles and forums just soaking up all I could.
It started as a fascination of what the human body could achieve and turned into a passion. The wait was mostly due to reluctance to alter my natural homeostasis and cause permanent damage, or even temporary damage really, which I managed to do as well...
Dont use steroids unless you've plateaued and are willing to sacrifice some significant comfort in the future. Weekly pins for trt sounds like its nothing, but man...after years of it you realize you've become a slave to the stuff...
There are alternatives to injections for trt but I just don't feel the same, creams suck ass..

Dude, no....look train for the next few months plus naturally. EAT A FUCK TON. Not shit food but good amount of protein 250g minimum every day, moderate carbs and fats. You will gain without gear. While you train do a lot more research. Grab a pen and paper, take notes. A plethora of information here.

The fact that you are asking questions 3 through 8 indicates you need to learn way more before you start if you want to have a successful cycle... which answers question two. You should wait.
For now, learn about diet, make sure you have created a good, disciplined, exercise routine. Learn about half-life's, Get a blood test before you start to tell you what your T levels are. This will be your natural baseline.

You are 145 lbs, I'll give you 150 on a good day. That means you are not eating. Steroids don't make up for a shitty diet. You can put on an easy 20lbs without any drugs.

You didn't mention how much you eat or training style used. You can take all the drugs you want but without food nothing happens. But if you're determined to do it anyway. Have your Ai on hand and get bloods at 6 and 10 weeks especially in your first cycle to check test and estrogen levels. Have pct on hand in case you have to abort the cycle. 12 weeks 500mg per week pin Sunday and Wednesday works great for me.
Get a 2nd box of just needles i like 25 gauge 1.5 inch. Draw with your 23 and inject with your 25. Pinning with the same needle you draw with hurts and can cause infection sometimes. So always pin with a fresh needle. I always shower before injection. Just as.a secondary precaution. Use 2 alcohol wipes to clean again let fully dry. Pin then clean again. Be safe learn side effects to watch for and be nice to the vets around here they can really help with things. Especially rusty and makwa.