Permanent suppression from a cycle of testosterone is virtually unheard of, even more so as an 18 y/o. PCT is NOT a requirement, even if you are coming off completely; it make take a few more weeks, but you will still rebound. Fertility is a nuanced topic, but I personally don't put too much thought into it given the resources and science available. HCG seems to be the most sustainable and accessible way to preserve testicular function. I recommend 1500IU a week, either year round or every 12 weeks.
The most important things you can do is get blood work as often as you can afford, ideally a basic panel every month (CBC, CMP, Lipid, E2). The other complication that is much harder to monitor is LVH, but can be done through an echocardiogram, though I've not found anywhere that doesn't require a referral from a doctor, though YMMV.
Regardless of what you choose to use, try to be objective and introspective about how they effect your physical and mental health. Don't be pressured into taking more stuff from how other people look. Always try to learn and improve your understanding of things, regardless of what you've been told or you've experienced.
Also, don't use PEDs if you're competing at an amateur level where most people are natural. I think that goes without saying.