1. GoodSync Explorer (recommended)
2. CarotDAV: (basic)
3. GDocsDrive:

These softwares make multi-user experience better, reducing harassment of logging in & out frequently.
If you have time to set it up, you can have unlimited Google Drive storage space COMPLETELY FOR FREE!!!

What you can do is open multiple accounts and put all the files from all accounts in a folder for each account and share each folder from all accounts with your main account. In that way, all of the files from different accounts, can be accessed from one single account, your main account.

But, there's only one trick, you would have to sign-in and sign-out/switch accounts quite frequently if you upload big files frequently and run out of space in one account. That's only one downside, but, if you can't afford to pay, it's totally worth the account switching times.

  1. Create a few accounts, for example let's take 3, goog.drv.001, goog.drv.002 and goog.drv.003
  2. Share these two folders: "goog.drv.002" and "goog.drv.003" with the primary account, goog.drv.001, so they appear there. 
You can access them but not upload from the primary account, if you do, those files won't be hosted in the corresponding accounts but rather in the account you arelogged in at the time of uploading. Keep in mind that these are just folders shared with this account, in order to be accessed by you, not whole accounts.

In order to upload and store files in the other accounts' space, you have to login there and then upload. Then those files will appear in the primary account.

One way of doing this without harassment is staying logged in to the primary account on your browser, and when wanting to upload to other accounts open an incognito window. Another way is using third party softwares which can allow accessing and uploading files from multiple google accounts.

So, in this way you can add an unlimited number of accounts, thus, an unlimited number of GB (storage space). All you have to do is open as many accounts as you wish. To do that you will need to change your IP constantly, for that I recommend free version of CyberGhost VPN. Maybe you might need to change your browser too, as well you will need multiple phone numbers to confirm the accounts, just use your friends' or family members' phone numbers.