I you're keeping yourself natural, remember that the body grows in waves. In each wave, you'll work to consolidate your gains. The average amount of lean mass a normal man can amass that way is 2-3 kgs per year. What does consolidate mean? It means the mass that you have added to your body becomes your new normal, and your body will understand that it's necessary to keep it, or recover it faster (muscle memory) if you lose some of it due illness or some other event.
What happens with newbies the most is that the young ones start injecting a lot of crap in their bodies, then they add like 10-15 kgs on their frame in 2 months. Then, as they stop cycling, they lose like 90% of it, or more. The psychological impact of that will compel them to start over, then you have steroid addiction pronto. That happens because the body sees no necessity of maintaining all that surge of mass like that. There was no time to consolidate anything, not to mention if their training was not really high in intensity, it's even less of an argument to convince the body to keep mass otherwise either.
Whenever you hit a plateau, it means you have to shock your body into learning that it needs adapting to something harder or heavier. The most common thing is loading progress, but you can also squeeze another set within sets, start adding cluster sets, advanced lifting techniques (avoid failure on all sets, btw), FST7, partials, plyometrics. There are many tools at your disposal for shocking your body into adapting and growing to address these new intensity programs.
Some muscles respond better to partials (for hypertrophy terms) from a stretched position, than others (triceps, pecs, biceps, calves, lats). Some muscles respond better at low reps, slow and heavy lifts into a failure sensation (legs, some rows, traps). Others, to higher volume, reps and sets into a burning sensation (shoulders, forearms, calves, serratus).
Mobility training is extremely important to do too, specially if you're starting a lifting lifestyle. Or you'll have to address all the fuck ups you did during your life later, as I'm doing now. Back then, mobility was not part of gym vocabulary. It'll help you keep your joints and tendons healthier for longer.
Try not to compare yourself to others too. People have different muscle bellies, different muscle insertions. Sometimes, our body is not that 'nice-looking'. It's also not something that can be changed by putting on mass. But, sometimes, it gets harmonious and ok-ish. But do not think that your shortened biceps will ever look elongated as the next guy's elongated biceps. Each one has your own physiology.
The rest of things I would suggest you to look into seems to have been addressed already by other members, such as proper sleep, proper food, supplementation of what works (creatine, betaine, omega 3, some form of protein shake if you need a plus, vitamin D, B, magnesium, zinc, electrolytes, leucine), proper rest and periodization. You need to assess your body to see if it responds better working more frequently, or more paused-ly. Even after 23 years of gym, my body responds better working a muscle group at least twice a week, in a push-pull lower-upper scheme. Once a week does not go well with me, and it's true to MOST people as well. The usual subjects that benefit from once-per-week routine are usually experienced bodybuilders and powerlifters – strength training requires more rest. Tendons and joints are not as flexible in training nuances than muscles are, and you must protect them.
That's all that's safe to advice/educate you on a holistic note from my expertise.