Does he already have a good controller or headset for online, or is everything still stock?
If the accessories are sorted, then games are your safest bet. With your budget you can grab a few fresh releases or one top-tier single-player. Shooters and action games come out regularly, so there's plenty to choose from - check what he hasn't gotten around to playing or what he's mentioned. PS5 games vary in price, but you'll definitely find something solid for 5,000-7,000 rubles.
For accessories, a quality headset makes sense if he plays online multiplayer. Or a controller with haptic feedback - the DualSense opens up a lot in terms of feel, but the standard controller is pricey. A charging dock for controllers is a small thing, but handy.
If you want to go beyond gaming stuff, anything he actually uses: quality headphones for music, a comfortable chair for long gaming sessions, figurines of characters from his favorite games. The main thing is that it's something he wouldn't just buy himself because he doesn't think it's worth spending on.