Werd. Figure out the type you want to do the most. For road racing get involved with Solo II, then lapping and Solo I I'll breifly describe how I got involved with racing, applied to rally, maybe some drag dudes could talk about that particular pursuit.
How to get started in rally without wasting an ass-ton (approximately 2.2 regular tons) of money
Step 1 - find club in your area. SCCA still does road rally, Rally America does stage rally. People will cross over between both. You don't need a membership to start, but it's good to make contacts
Step 2 - Run some Time Speed Distance (TSD) events. While many people find them boring for the driving, you will learn a lot about how rallies operate. Any potential Navigator/ co-driver you have in mind will figure out really quickly if they are prone to losing their cookies in a car and how much they trust having some loose nut at the wheel while they have no control.
Step 3 - Go marshalling. Working at stage rallies will give you insight as to how timing works, procedures, etc. Again, you will learn a lot, make really good contacts and get to see the cars in places regualr spectators don't get to.
Step 3A - If you are good mechanically, get involved with a team and crew for them. You won't learn as much about rally procedure, but you'll learn a lot about what breaks on rally cars (I'll let you in on a secret - everything breaks)
Step 4 - Co-drive. You can start co-driving for under $1000, and if you're good, you will be in demand.
Step 5 - And this is the most important so listen up:
If, after all that, you want to take the plunge and feel the loose gravel under your tires and the wheel in your hand as you rocket down a stage road then, for the love of God and all that is holy, DO NOT BUILD YOUR OWN CAR!!!!! BUY ONE THAT HAS ALREADY BEEN BUILT BY SOMEONE ELSE AND HAD ALL THE BUGS WORKED OUT!!!! Used rally cars go for a fraction of the cost of building. I've seen some nice ones go for the cost of a cage alone.
And if you think I should just leave it as a dream then feel free to say so.
I personally feel there is no good excuse for people to not go racing, if only at the solo II level, if that's what they really want to do. Don't be that guy that sits on the sidelines and dreams.
"It is better to have raced for a minute than to have spectated for a lifetime."