Back to the original question....
You definitely have to participate to get more followers. Just posting photos won't do anything.
First: Be selective in what you upload, only upload the best shots. If you go out for a day trip and take say 200 shots, only upload the best 2 or 3, if you have more than 3 shots, upload them over a few days, not all in one go.
Second: join relevant groups. If you like wildlife, landscapes and street photography, join a few groups for each type of photography. Then add relevant photos to the group as you upload them, but not too many at once. People interested in that style of photography will see your photos, fave them, comment and if they like the rest of your stream (if you are consistently uploading stuff they are interested in) you may get more followers.
Third: Go into groups that interest you (and browse explore) then when you see images that you like, fave, comment and if you like the stuff they are uploading, add them as a contact, you might find they add you in return.
I've found some groups much more friendly and more likely to interact with you. This is particularly true of "challenge" type groups, like 365 groups, 52 weeks groups, Macro Monday (they always get photos in Explore every week) or 100 Strangers.
It's just like forums, you get out more the more you put in.
