im about to invest in a bit of bitcoin as well as other cryptocurrencies such as eth, ltc, etc. Im thinking about making a wallet on a usb drive for a start. ive read about electrum but need something for all my crytpocurrencies.
THe hardware wallet seems to be a recomended choice for you, or you can try to download the multy currency wallet just like coinomi and jax and then you can try to turn your mobile phone off.
YOu already made your own offline wallet.