So, I have searched the Stack Exchange and I found what I CANT do but sadly not what I CAN. What's the safest way to login in your accounts (Gmail, Google or even your eBay account) without breaking down your anonymity? Many said that some sites have their ways into tracking you down, thats true, btu does this mean I can't never login somewhere without betraying my location?
Logging into accounts associated with your identity is inherently not anonymous, but Tor will still hide your physical location (i.e. what internet provider / Wifi hotspot you are using at the time) from the sites.
However, you should not mix logins into sites associated with your identity with anonymous browsing in the same Tor Browser session.
This may not be exactly what you are looking for, but hope that it can help you to get some basic ideas.
An attack called Correlation Attack can be employed to trace where you are if the Autonomous Systems between you and the Guard node, and the Autonomous Systems between the Exit node and the final destination are controlled under one person (lets assume: maybe only Government Agency like NSA, CIA or FBI has that kind of power)
However, if you are using gmail, facebook, hotmail, I do recommend that you should create those accounts in Tor environment without providing any real information about yourself, and only log into those accounts within the Tor environment.
For this task, you may need a temporary and unregistered phone number to verify the account. Since most of those services like Gmail and FB will ask your phone number while registering via Tor to send a code for verification purpose. After creating the accounts, you should destroy the SIM card of that phone number and never use or register the phone number if you want to stay anonymous.
P/S: if you log into your account from a non-Tor IP, then the next time you log into the account via Tor, your account may get blocked. So do remember that if you create the account from Tor-IP, then next time you log in, your account will not be blocked. For your ready reference, here it Onion site of Facebook, you should create an account from this site so that your account will not be blocked or ask for some secret question or verifying some friends' photos. https://facebookcorewwwi.onion/