Sounds like you want to keep pictures to hand on your camera, therefore you should go for the largest card you can afford.
Given you've posted in the D3300 forum, you won't need a 2nd card for the 2nd slot, so the choice is yours if you want a backup card.
RAW images are much bigger than jpg's so consider that also when deciding the size you're after.
With regards to backup - copy to another device (PC) often as you can in case of any card failure.
As to finding your pics - I think the D3300 allows you to view by date so that might be the best option to show your pictures if you want to use the camera's LCD screen to do so.