When I started I drew a diagram of the chain and it helped with the basics - there's obviously more to it that that but I hope it can help
Outside tap - ro - water butt - submersible pump and hose - van mount tank - pump inlet - pump oulet - di - hose reel - pole
plenty of thread tape on connectors - use decent ones -
fit the pump with the hose connectors at the bottom or lain flat - if they are on the top and you get a leak they could foul the electrics
use stop connectors wherever you are likely to have to break the hose - to pole etc
you might not need to pump your water if it's a smaller tank - you could just fill smaller cans and fill the tank manually