I've done a few major projects. I always set up a plan. Some things need to be done before you can do the next part. if you get them out of order, you end up dissembling something to do what should have been done before. After you have to redo stuff a few times, you learn to follow the plan.

1) Determine what kind of a vehicle you want to end up with. A fast race car, and a great driving car are different vehicles, mixing the two usually results in disappointments on both ends. Picking one direction or the other often provides a less strenuous budget. A build may be limited by a financial budget, and/or by a time budget. Its important to pick one style and stick with it until the end. Changing direction in mid stream is costly in both time and money. If you still up in the air, pick the direction that will provide the most useable pleasure for you and your family. You can build the next project in the other direction. I see guys with 3 or 4 cars, all about the same, that are still not happy. Thsat is usually because they tried to mix the uses of the vehicle. If that is you, build the next project with one simple goal, and go in that direction to the extreme.

2) Determine what needs to be done to reach the goal for #1. Example, I'm looking for a great driver. I have a 44,000 mile drive train in great shape in my current build, other then replacing gaskets and seals, and replacing wear parts (water pumps/fuel pumps), it doesn't make a lot of sense to rebuild that drivetrain unless I expect to put over 100,000 miles on the completed ride. With the more then a dozen rides I've built, only 3 ever exceeded more the 60,000 miles after they were roadworthy.

With a single direction, and a list of what needs to be done, you can create a plan that will reduce the back tracking, but that process is a learned process.

Process: Always secure the parts you are going to need for the next step in the process. If you encounter a rare part, or get an astounding deal on something you will later need, pick it up, but generally, getting more then 2 steps ahead of where you are in the build causes issues. You don't need new tires or wheels until its almost driving time, old wore out tires and wheels of the correct size work well for the building and moving around process..
1) Build the chassis.
A) Clean up and repair (or modify) the frame (or under carriage if unibody).
B) Rebuild, replace, or upgrade, the suspension (everything in the front and rear), the brakes (everything involved with the brakes, master cylinder, booster, brake pedal assemble {and clutch pedal assembly if applicable} hard and soft lines, wheel cylinders, calipers and E brake). Make sure the system remains sealed, but don't add brake fluid yet. Buy new lug nuts for the wheels you will be using.
C) Prepare the rear axle Gears, seals, gaskets, bolt it and the rear suspension onto the frame. Make sure it travels freely and smoothly through the suspension travel without binding. Check the suspension travel without the shocks attached. Get the new shocks (all 4 if you haven't already). Old tires the size you intend to use that hold air (for at least an hour) on wheels with the correct off set work good to make the frame a roller. You can check to be sure the tires clear everything on the full suspension travel (again without the shocks attached). You also notice no paint has been applied anywhere yet.

If what you are building is an original car with minor modifications, most the the next few paragraphs will not apply. this is for the more complete custom route.

With a rolling chassis, if a separate cab/body is involved, you need to position the body in the place it will reside on the frame. You need to locate the firewall where it needs to be, you need to determine the height of the body in relation to the frame, and you need to determine how the body mounts attach to the body and the frame.

Once the body location has been determined, and the firewall location is known, installing a mostly complete outer shell of the motor & trans are needed. By that I mean you need a block with heads, valve covers, a water pump housing and water pump (the pullies, fan, alternator & brackets, are also helpful) and the oil pan you want to run (oil filter and oil pump if external as well). All this needs to be bolted to the trans case (manual or auto) you are using. Hang the motor/trans in location to determine the motor mounts/trans mounts & trans crossmember locations. Adjust the motor location for exhaust (headers or manifolds, and pipes).

If your building an existing car or truck that used factory stuff those steps are pretty straight forward.

Once everything fits and clears, pull it apart and paint everything, including the under the hood panels. After the paint has cured, carefully assemble the chassis & bleed the brakes. Install all 4 shocks. Then you build the motor & trans, be sure its build for best use with the intended finished outcome determined in Step # 1 and Step #2. Unless the intended outcome was an all out race car, do NOT build the motor as such. Slightly over stock production power level works well for a driver, too many over build a motor and end up with something that is not fun to drive on the street. Race motors have poor daily driving manors nearly all of the time.

With the motor & trans in the car, its time for the new tires and wheels. Gene