Hello as the Subject implicates, I would like to know which is the best online BTC in order to store my BTCs. I know some software wallets like Electrum but I would like to have an online in order to access it from anywhere.
As everybody already said, storing Bitcoin online is unsafe.
So, using online wallet makes sense only for small amounts.
Now, depends how you achieve your Bitcoins. If you bought them for fiat or got them from exchanging some altcoins, it could be an idea to just keep those Bitcoins at the service you already have them so you don't pay extra transaction fees, especially if you plan to achieve more.
Also it depends on how you spend. If you want to spend often, find a wallet with low fees. If you don't want to spend at all, securely generating paper wallet and storing your Bitcoin there is a pretty good option too.\
And since you wrote that you want to access "anywhere", one option better than online wallet could be a mobile wallet, since your phone is also always with you. But this is a subject others explained already well enough.