My Raspberry Pi gets to slow to login while loading blockchain

Hi all ! Im new to this forum and have had great help installing my reddcoin-cli on my raspberry pi3 (loads of thx) but i´ve run into some issues that i hope you can help with. Im almost done with the blockchain but had to reboot the pi 4-5 times cause (i guess) the memory isnt enough. I have a swap file (1gb) on my sd card but was thinking that i might be better of using a 16gb usb and swap that one, maybe 2-4gb, whats ur opinion on that? when the blockchain has loaded a couple of hours i cant even log in to my pi (using ubuntu mate). I am in the learning progress of linux so if u think i should use a usb, a little howto would make my day. Or if u have another sollution on my problem, or will my problem go away when the blockchain is fully loaded and i start staking ? For now i just wanna load the blockchain enough to get my coins.

I hope im not to blurry about my problem, all help is very appreciated.