First, fix all the problems with the parts you are going to keep. But don't sink any coin into stuff you are not going to use. This is part of the make it safe with cage, belts, etc.
Now as you follow your plan (you do have a plan on what you want, don't you?) take care of the non-functional items first with the upgrades.
I would love to be more specific, but there are countless versions of a "trail rig". I have seen trail rigs that are nothing more then a stock truck with cut fenders, big tires and welded diffs all the way up to tube buggies that have a little bit of a Bronco grill left on them. You mention ARB, do you want that in a D44 or a D60? That is providing you were talking about the front. Rear, stock 9" or 1-ton? Full width 1-ton, full width half ton, or stock? Pure trail or drivable to the trail? The above answers and I am sure some that will follow will be good plans, for what the poster is thinking their idea of a trail rig should be. But do you want there idea of a rig, or your own? It is easy to follow someone else's plan and build something that doesn't work for you. It is another to determine the parts you want in then ask us what order to put them in.
I think you want us to tell you what order to do the work, just what work do you plan on doing?