You are under no obligation to follow someone. You certainly can if you like. Following those that you think you can learn from is good and those you are friends with.

There is no requirements but, that is how we meet people here in the community and we follow and share, They are just welcoming you, If you get the time, and want to make contact just send them a little note and say thank's for the follow,and it is nice to meet them or something to that effect.
You will probably get a lot of them from all over the community, We share and communicate an ask questions and just let them know we are glad they are here.
It can be a bit overwhelming when you first star out, Your priority is your reason for being here,that is to follow the lesson and concentrate on learning how to build your site, and after you get a little more use to the surroundings it will be easier for you to communicate within the community
Here is a post that Bo wrote maybe it will help
https://my.wealthyaffiliate.com/bothewebguy/blog/following-following-back-at-wa

2 options:

1) follow them back if you want
2) do nothing