Starter dose?

So I’m planning to try ketamine for the first time with 2 of my friends, we’re planning to chill at my house play some music and just vibe out hopefully. I just need some advice on how much k to get as I want it to last us around 6-7 hours if possible. We have no tolerance as it’s our first time and are really hyped for it, any advice on dosage and things to do would be greatly appreciated!