Well, first off, I don't know if you are actually asking this, or if it is just a really old post of yours you brought back to the top for old time's sake, but here goes.
From here, you have two options, one will come in under $35k, the other may require you to race the Turbo/NA (whichever one you upgraded the Miata with) a couple of times.
1. Buy a Lexus IS (Toyota Dealership), and some upgrades (you shouldn't need too many), and win the Amateur Altezza cup (make sure to save after 4th race, exit the 5th, and repeatedly re-load your game until you get the Altezza LM Race Car). Now, if you wish, use the Altezza to beat the last Altezza race in Amateur, and use it to quickly win the Altezza cup in Beginner (sure, it may not be challenging, but you already proved your mettle by winning the Amateur Altezza Cup, not that I care about being fair, but you might
).
After that, to come up with money for dirt tires and the highest engine upgrade, race either the American Amateur Championship, or the Euro Championship, an use the save before last race trick to win the most expensive car and sell it (the Camaro Race Car at $250,000 resale, and Gillet Vertigo at $300,000, respectively). Keep in mind that if I remember correctly, the American should be easier (I don't remember what cars you'll be facing in Euro, it may be easy to, but I remember that you should have a pretty easy time in the American Championship).
Now, buy the best engine upgrade and dirt tires for the Altezza (it's a race car, so everything else is taken care of). After that, it should be fairly easy to win all the rally races (you don't even need the engine upgrade to be honest, but getting the engine upgrade is easier than trying to win the rallies by actually racing, instead you can just generally aim the car and floor it with the gear ratios set to acceleration, of course make sure you have an OK 6th gear for the straights). Now, you have the Escudo, and several options open to you, you can either get your S License and win the Like the Wind race, netting you a 787B, or you can try Super Speedway and risk the 1/4 chance of getting an F090/S. Keep in mind however, that if you get the 787B, you can win the Dream Car Championship, and use the save-before-last race trick to get an F090/S. Another option that doesn't even require the Escudo (but does require your S License) is winning GT World Champ. in Amateur, and taking your GT-ONE + Super-Slicks to the Polyphony Digital Cup to get an F094/S (best car in the game). But whatever you do, that strategy will get you pretty much all you need to beat the game (remember the Euro/American Champs if you ever need money to buy anything after that, and the game should pretty much be yours from there on).
2. The other option is to buy the SLK230 Kompressor, race the Beginner Silver Arrows for upgrade money if you need it, and then win the Amateur Silver Arrows for the CLK Touring Car. From there on you can race the American Championship to get money as described above (save 4th race, reload until you get Camaro, sell for $250k). Or you can win the Euro Champ. to get the Gillet Vertigo, which you may want to keep, since it is fast and handles excellently once tuned. Whatever you do, once you get your hands onto the race cars, you should be able to get whatever cars you need from there on to beat the game.
So there you have it.
