Hi I have a 2000 sc300 all stock. I was wondering if there are any performance mods that can be done that wont break the bank. Im on fixed income but hav some money to do things. Thank you

 

A perfect running car makies optimum power. So if you are due for a timing belt, waterpump, sparkplugs, do it. Refresh EVERYTHING. If it leaks oil from a valvecover gasket: Change them.
Replace the spark plugs with Denso iridiums.
Replace both of your primary O2 sensors for new ones.
Replace the VVTI solenoid (they are wear items and only last 100k miles.
Are you running conventional oil? Switch to synthetic blend. Run that for a full year then switch to synthetic.
Change the trans fluid. Toyota Type IV. Buy a case - 12qts - and do 3 drain and fills in a row. 1000 miles apart. That's basically a trans flush without using a machine, and this method will replace 75% of the trans fluid with brand new fluid when you're done.

That said, the next thing that can be done would be a BFI mod. That's free and actually works. There aren't any aftermarket intakes that add more power to these cars than modifying the stock airbox does.
After that would be the exhaust. If you want something that sounds louder off the bat, unbolt both mufflers and go for a drive. If you like what you hear, extend the exhaust piping back from the resonators to the stock muffler exit points. The majority of people usually just delete the resonators. This gives the car a low growl on accel but no drone or exhaust noises while cruising.

 

The next steps after what I listed above is where things can get expensive fast.

Start with a 3in catback exhaust. Building one yourself will be cheaper than buying one. But buying one complete saves time and frustration.
Now if you just want a nice growl from the motor and you want the car to be 100% reliable so you can do other things, like other mods or just enjoy the car, then I would suggest getting an IS300 exhaust manifold. It will replace the stock manifold and delete both front cats. It will probably leak at the flange gaskets so you're going to have to get a little creative solving this issue. You will also need to put spacers on both rear O2 sensors to prevent the car from generating CELs. Once you get a header, you can also buy a GS300 Y-pipe and modify it to replace the stock SC300 Y-pipe. You will need to alter its length to fit on a SC. When you are done you will have a car that sounds really nice, makes about 20whp more than it does stock, and will be 100% reliable. And it won't cost anywhere near what a turbo kit costs.

There are no cheap turbo kits for our cars. People that say they're going to turbo their car for $2k always end up at 6k-8k in no time. You said you have some money so if you would like to turbo the car I would just suggest doing all the maintenance I listed in the post above, then just start saving money. Once you get about 6k pooled together you can start piecing together a turbo kit.