Hey DarkFeathr welcome to The West
Tribe/Clans here are called towns and alliances. Once you've joined a town it's more than likely that the town is in an alliance.
An easy way to see which alliances are better ones is by going to this link
http://tw-db.info/?strana=politic_map&world=en16 which is an alliance map of Dakota. It shows which areas alliances own on the map. Above the map is the top alliances and the towns which are in that alliance.
Message a founder or councilor from whichever town you want to join in the alliance of your choice. Founders can be seen by clicking the town, pressing on the Town Hall then choosing residents. Founders are seen with a black hat and councilors have a grey hat.
Like a Sir is correct, it's better but not necessary to level up to around 20-30 but some towns accept any level. If you ask for an invite to a town and they don't want such low levels, they may re-direct you to another town in the alliance which is more suitable.
Most people here are friendly so I'm sure you'll get accepted into a town without any worries.
In your message, mention that you're new and need help learning and that's a guaranteed way that you'll get in and they'll help you with all the questions you ask.
Hope that helps
sambee