GURLS is a generic roleplaying system designed to be versatile, fluid, and tactically nuanced. The timing system brings a world of depth to everything a character can do, while keeping things simple to understand and fast to execute.
For some reason every RPG rulebook I've ever read has a "what are you doing here" section. You're playing a game. I decided it'd be better to put out an answer to a question that nobody agrees on the answer to in order to rile up the internet.
A roguelike is generally considered to be a video game featuring procedural generation and permadeath. This game is not a video game and I guess you could make a system in it where you don't die when you die. So why am I calling this a roguelike system?
The game Rogue and its decendants are unique among RPGs in their non-modal movement systems. Instead of allocating a number of things that players can do on their turn, you do one thing at a time. It could be movement, attacking, drinking a potion, pulling a level, opening a door. Some games have combination actions, but those are typically still oranized as a single action. While you're doing your one thing, everything around you gets to do things.
GURLS works like that, and because of this it's pretty easy to convert the simpler roguelike systems to tabletop. The first playtest used an almost entirely unaltered DoomRL ruleset.
A full set of play dice from 4 to 20 sided should be enough, but more is always helpful for large rolls. At a minimum you should have two 10 sided dice.
Paper for noting down turn order and results is also HIGHLY reccomended because of how turn order works. Don't worry, it's simple. Having notes by everybody also helps make a timeline of events for the game people can easily look back on.
This is a basic rundown of the system that will allow you to adapt almost any other system to this core ruleset. While I've made some specific adjustments to systems to make them flow better in a tabletop setting, the core should be playable. Always remember that the GM has final say in everything, and if they contradict a rule mentioned here they're doing it to make the game more fun so listen to what they say.
The core mechanics you need to know are Turn Order and Dice Rolling.
Turns in GURLS are different in that everything you do takes up time. The gamemaster(GM) will announce how much time has passed, and if you'd like to do something at that point you can tell the table what you intend on doing.
Generally the GM will count upwards from 1, to 2, to 3, and so on until a player pipes up or they announce that something happens at that point. In combat this is usually seconds, but for other tasks it can be minutes, hours, or even days.
Most actions have a defined amount of time. If it doesn't, the GM will tell you how long it takes. If it does, the GM will also you what the roll is and what you need to succeed. In general, you can interrupt actions that don't require rolls at any time by just stopping doing them. Actions that require rolls generally cannot be stopped.
What dice you roll depends on the system you're using. For generic RPGs you can assume a d20 for skill rolls + whatever bonuses you have. If you roll higher than what the GM tells you you need in order to succeed you pass and get to do what you wanted once the time has passed. If you fail the GM describes how you messed up. You should try to do all your rolling before the time has passed. Many skill rolls(such as attack rolls) have you also roll for effect if you succeed. Since you should always know what it takes to succeed, you can do this while other people at resolving their turns to speed up the game.
Occasionally the GM might not tell you what you need to pass a certain skill check. In these cases you just tell them the result. Occasionally the GM might also roll for you to keep the results hidden. For instance when you try to lie about where you were the night of a murder, the GM might not want you to know if the police believe your story.
And that's all you absolutely need to know. The rest can be entirely up to you. I'll link system specifics in case people want to use them, but feel free to make your own or adapt an existing system.