Need help with Cloud Storage

Hello everyone! I have a problem with Dropbox and I wonder if anyone can help me to resolve it.
I used to love Dropbox (I still do, but not so much anymore) - it kept all my files synced and accessible from anywhere, on all devices. After using it for 6 months I purchased additional storage and I think right now I am up to 150 GB of space. Which is cool, because I am only using 50 GB or so.
However... you know how small SSD drives are on Apple Air. Even on Mac Book Pro. In the last 2 months I have updated Flash drive on my Apple Air, storage space on my old Mac Book Pro 17" and I just recently purchased Mac Book Pro Retina 15" with 512 GB. I thought it would be enough for a while. But it is not. First of all, I had to install Bootcamp and after downloading Dropbox under Windows I only had 99 GB left. Which is not that bad... but somehow the idea of going under 100 GB makes me uncomfortable.
Sorry for the long story. I guess I just want to say goodbye to Dropbox all together and have my personal server or my personal Cloud Storage.
Any recommendations?

Thank you!

Any cloud solution that syncs your files will take up space on your local machine (which I assume is the issue you have).

You can stop Dropbox auto syncing certain folders like this

What if I was to set up a server? Could I set up a server with Mac mini with OS X Server? I am on FIOS, so file transfer would be fast-ish.

To do what exactly? You haven't really said what the issue is.

Yes, I did. The issue is that I run out of space. I had to actually get an external hard drive and to move Dropbox there. I want to have all my files in one place (not on my hard drive) accessible at any time and synced between devices (Mac, PC, iPad, iPhone).

Sorry, I thought you had 99gb free, not that you'd run out of space. I must have misunderstood.
You can't have files synced between devices but not on those devices. That's not syncing.
You can store things in the cloud so they are accessible on all devices, ie the way Dropbox works on iPad and iPhone and as per the link above. That way you aren't using local disc space. But the files won't be 'synced' and won't be available offline