Hopefully this helps - I did a breakdown of my manifold for someone else in my build thread, so it might help when thinking about yours. One thing I wish I would have done was bump everything to 1" instead of 3/4" PVC, otherwise the rest is relevant and referenced in the pictures below.
So I'll start at the Vectra and work towards the red sea return pipe (threaded potion only).
Vectra union (comes with the pump - its the blue ring)
3/4" red schedule 40 pvc
3/4" dual true union ball valve
3/4" red schedule 40 pvc
3/4" 90 degree slip/slip elbow
3/4" red schedule 40 pvc
3/4" "T" slip/slip fitting (3/4" red schedule 40 pvc - 3/4" union - 3/4" red schedule 40 pvc - elbow - 3/4" to 1/2" adapter - Reactor)
3/4" red schedule 40 pvc
3/4" "T" slip/slip fitting (3/4" red schedule 40 pvc - 3/4" slip/slip Gate valve)
3/4" red schedule 40 pvc
3/4'" "T" slip/slip fitting (3/4" red schedule 40 pvc - 3/4" slip/slip Gate valve)
3/4" red schedule 40 pvc
3/4" 90 degree slip/slip elbow
3/4" red schedule 40 pvc
3/4" 90 degree slip/slip elbow
3/4" red schedule 40 pvc
3/4" 90 degree slip/slip elbow
3/4" red schedule 40 pvc
3/4" threaded male adapter (about 15-20 wraps of teflon tape)
Red Sea threaded pipe