I hate to be a na-sayer, but if you don't know what you are doing, I don't think your 4runner is a good place to learn...
I am all for people learning new skills, and wanting to join the addiction that is metal fabrication, but on a vehicle is one of the worst places to learn.
We put our 4runners through a lot of hell, and if something is welded poorly, or poorly designed it can lead to more damage than you think. Plus there is no money savings from building. The equipment is expensive, the time cost is very high, and the learning curve is expensive (I have learned all of this from experience). If you are not a competent metal fabricator I highly suggest buying quality parts you can use instead of creating a ton of headache for yourself. I have seen countless projects sidelined or not completed because people got in over their head very quickly. People buy cheap tools trying to save a dollar and end up with subpar parts and end up having to do everything over again, or they just give up.
Then there is the safety factor. Poorly built parts can be very dangerous for you, your passengers, or others on the road or trail. Suspension or armor parts can break if built poorly (even pro stuff breaks) and can put you in dangerous situations. Or something as simple as a skid plate can kill someone else on the road if a poor weld breaks and it falls off your rig at highways speeds. I have seen this happen, it's never fun and the couple dollars you think you will save is not worth the risk to yourself or others.
My suggestion, buy quality parts for your rig from reputable builders. Nobody on here will look down on your for buying parts instead of building them. We will all love your rig no matter who builds it, if it is nice, it's nice. I build parts for mine and I say all the time how stupid it is, how I spent too much time and too much money. That I only do it because I have a weird love of doing it and that it's something I truly love to do. If you are really serious about it, my advise would be to learn from the pro's. Take a class at your local community college and get certified in welding so you know how to do safe welds, and know what the right equipment to use is. Or go find a small mom and pop shop that does metal fabrication and ask to be the "shop bi*ch" so you can learn from a professional how to do it. That is how I learned, I put in countless hours learning from people who know what they are doing and now I have the knowledge to do it myself. I spent over 10 years doing it professionally and I still learn new things every day.
Sorry if this is long and not what you are looking for. I just want to give you the tools to be safe and also have fun... Good luck either way.