Do you have a Jiu Jitsu buddy?
Training at a gym without knowing anyone is difficult. You need to be friendly with everyone and you need to break into a place where people already have formed cliques.
If you can get a friend to train with you, that would be great. You're both learning and progress at the same rate, you get to try new things on each other and if you fail. You fail together.
You create a strong bond with them and you trust each other. Thats really the biggest thing. You don't know who you can trust to not just break your nose when you're training.
So if you don't have a buddy to train with. Become friends with someone similar level to you and try to match the days they're training. Not in a creepy way. But you want to have someone who can be a great training partner.
Of course you can't stay with them forever. So you have to eventually become friends with other people. But for the initial start. Get yourself a jiu jitsu buddy.
Having friends on the mats helps a lot. It turns training into a social event where everyone is on the grind to improve themselves. It's great.