Rec Room

2024 Update notes: Holy smokes, who would've guessed this solution would become such a behemoth. Thank you to all people who contributed in the comments. This will be the only update.

Warning this achievement takes around 108 days to complete lvl0 -> lvl 50, LPCastle also notes it takes 72 days to go from lvl40 -> lvl50

Note to people who are going for 100%:
As pointed out by: KinectKid333, there's always a chance this game will shut down before you get to complete this achievement. Please consider whenever or not it's worth the risk as the achievement takes 108 days. If the Xbox version stops to get updates you won't be able to unlock this even if you reach lvl50 on Steam.

- published on Rec Room official forums

To reach level 50 you need about 16k xp (8x as much time as it took to reach lvl 30).

https://images.squarespace-cdn.com/content/v1/5fa5929d1cf2d4......

2024 update: There indeed is a daily xp cap
It also seems like there is a cap to how much xp you can get every single day. This daily xp cap is mentioned on multiple forums. Either a cap or glitch which seems to reset every day. Please note your xp only increases after you left a room/new round starts. Some sources suggest resetting the game if XP doesn't increase.

My xp cap resets at 00:00 UK time, Max in the comments section said his xp cap resets at 20:00 EST

Level 0 -> 30 progress is in my "Rec Roomer I" guide
Starting off with: lvl 30.1
Day 1: lvl 30.5 ---- Day 14: 35.9 ---- Day 27: 40.45
Day 2: lvl 30.9 ---- day 15: 36.3 ---- Day 28: 40.60
Day 3: lvl 31.4 ---- Day 16: 36.75 -- Day 29: 40.73
Day 4: lvl 31.8 ---- Day 17: 37.2 --- Day 30: 40.87
Day 5: lvl 32.25 -- Day 18: 37.62 -- Day 31: 41
Day 6: lvl 32:6 ---- Day 19: 38 ----- Day 32: 41.13
Day 7: lvl 33.1 ---- Day 20: 38.45 -- Day 33: 41.26
Day 8: lvl 33.5 ---- Day 21: 38.87 Day 34: 41.39
Day 9: lvl 33.9 ---- Day 22 39.25 ---- Day 35: 41.51
Day 10: lvl 34.27 -- Day 23: 39.75 -- Day 36: 41.63
Day 11: lvl 34.73 -- Day 24: 40.03 -- Day 37: 41.85
Day 12: lvl 35.12 -- Day 25: 40.15 -- Day 38: 41.95
Day 13: lvl 35.5 --- Day 26: 40.28 -- Day 39: 42.09
Day 40: 42.23

Starting at level 40 you should be progressing at a steady rate of around 0.13 per day (A little over 1/8 of the square per day, or half a straight bar). If you finish the day with fresh lvl 43 for example, then the next day you can expect to be just past the first corner (about 3-4 pixels past)
2024 Update: LPCastle notes starting at lvl 40 it will take a little over week to level up, each level takes 1080xp. This can also be seen in the table above

To see your own level open your watch interface (menu button) and click the top left corner (profile). This will display your profile dashboard including what level you are.

Please Note:
This game is crossplay, as long as the game is linked to your email you can play on PC/Mobile and your progress will transfer. As long as you login to Xbox after you reached lvl30 or lvl50 the relevant achievement will unlock. If you want to be extra careful, login to Xbox the day before unlocking the achievement.

2024 Update: A good few times during the last year there were events that increased the xp cap or straight up removed it. Please is you see such event post in the following forum, comments tend to get lost on this solution

Strategy
There are 2 strategies found so far

1, Passive
- Join a community room (watch -> play -> select community in the right-hand side menu) The UI has been updated earlier on this week. Select Watch -> play and pick hot from the top bar menu to see levels where you can earn XP or recommended to play levels you joined before and afk for about 30 mins, after 30 mins leave the game and rejoin, repeat 4 times to get 2 hours play time (There seems to be a cap to how much XP you can earn at once)
LPCastle Update: Two 30 min games + one 15 game are enough to get you to reach the daily lvl cap

2024 Update: the rest of this solution can be safely ignored, the most effective way is the one above

2, Active
- Play 3 games to complete daily challenges + another 10 games to max out the daily xp cap. Results may differ, depends on how long the 10 games take

Some ways to get XP:

Daily login bonus:
Logging in every day grants you a small amount of XP.

2024 LPCastle update: Cheering, getting cheered and daily challenges do not seem to award xp

Cheering people:
Dpad left and up to select cheer, approach someone and hold LT. This will bring up a menu where you can cheer people. Limit 16 per day.

Getting Cheers:
If someone happens to give you "cheer" a notification will pop up. Confirm the cheer to get a small amount of XP.

Completing challenges:
There are weekly and daily challenges in your watch interface. Completing those challenges rewards you with an item and xp

Playing games:
Most important of all, playing games. I tend to stay away from team games like: paintball, laser tag, baseball etc. I find it easier to play solo games like: disc throw or quest games (^GoldenTrophy, ^CrimsonCauldron).
As pointed out by Max you should only play rec room original games or games with #RRO in descriptions, just to be safe hit the first icon in game filter menu (square box icon with some lines in it)
Community rooms do give XP now
With quest games up to 4 people work together to clear stages of enemies. The more enemies you kill the more xp you seem to get, hence if you are in a lobby alone start the game. Take it easy and let the enemies come to you. It's a one hit kill so be careful.
With disc throw up to 4 people compete against each other to get a disc from point A to B. Again if you're in a lobby alone, start the game.

Making rooms:
Probably the hardest one on this list. Make a room and publish it. If it's good enough people have the chance to like it (cheer), more people like the more xp you get. It's difficult for a room to become popular. Wouldn't waste my time on it.

CREDITS
Big thanks to all the people who helped me write this guide:

Cerberustorm
SwiftSupafly
qManballin
Maxumilli0n
LPCastle