Gaining lean muscle on 500mg test/week?

You probably meant: 'I've been trying to gain lean muscle for a year, now using 500mg test/week.'

I've heard 'time on equals time off,' but I might be mistaken. Time on plus PCT equals time off. I never fully cycled off since I was on TRT beforehand, so someone who runs full off-cycles can give better guidance.

When you hit a plateau, change something: train harder or less, eat more, improve recovery, or try a different training split. I believe in periodically shocking the body.

Either eat more or change your training — which do you think needs adjusting?

Calorie adjustment is step one. New muscle raises your calorie needs.

Agreed.

Don't run cycles longer than about 12 weeks — beyond that you're not doing much good. Eat right, get 7–8 hours sleep nightly. Spend a solid 6 months on gear then plan the next cycle. Test-only won't usually give massive gains; you'll likely need another compound alongside it for big results.

If you stick to solid nutrition even a beginner cycle should give good results. Prioritize bloodwork after a year on gear to check your health. Good luck.

Try starting around +500 kcal above maintenance and adjust from there based on results.

What's your full daily food plan look like? Carbs help shuttle nutrients so if you're trying to grow you need carbs. I ran 400mg/week on a blast and saw some size, hardness and got leaner, but once I ate more carbs I actually started growing. After PCT I kept 6lbs. I've been on TRT for years and did a PCT recently to reset receptors because my TRT dose wasn't giving great results. Also, when I eat 2+ meals and train vs fasting, I make better gains.

Why don't you want to add another compound?

I'd start with a small surplus, like +300 kcal, then tweak each week — maybe work up toward +500, and if needed even up to +1000 above maintenance.

Most likely it's either your food choices/nutrients, your training intensity or frequency, or a mix of both (that's the usual). 500mg of legit test should be enough for growth for most people. For six weeks lock in on eating a bit more and cleaner, train a bit harder or more often, and try to improve sleep duration/quality. Reassess after six weeks. If nothing changes then get a full blood panel (estrogen, SHBG, total and free testosterone, etc.) and start fixing specifics.