There's nothing wrong with working the RB20; sure, it may not have as much off-boost torque as the RB25 in the R33, but it can still go hard.
If you want to get some power, the first things to concentrate on are the intake and exhaust. Get yourself a decent cat-back system, a high-flow cat, a better front pipe and a split dump. For the intake side of things, get either a good panel replacement, or a pod and a heat-shield.
Support systems need upgrading too; a cheap upgrade is injectors from a Series 5 RX-7 (?), as well as things like an oil-catch can and an upgraded fuel pump. These things will prepare you for the next 'stage'.
After this, especially with the RB20, a new turbo is in order. The stock one can't be boosted much, nor does it flow much high in the rev range. Think R33 T3 or R34 T3. Both can be gotten cheaply, and, if needed, high-flowed. After this, a bleeder or (much preferably) an EBC (electronic-boost controller) (at around 12psi). Either a piggyback ECU (Greddy emanage) or a full ECU (PowerFC) would best go on at this stage, especially to stop the engine from running supremely rich (as it does when boosted above stock). Also, a FMIC (front-mount intercooler) should net you a few more rwkW's, and an aftermarket blow-off valve (atmo or plumback, your choice, but I'd go plumback) to stop the boost from leaking.
Now, you should be happily getting around 200rwkW's, should everything be set-up properly and nothing is wrong with the engine. Don't neglect to get better brake pads, and think about upgrading the suspension (Whiteline Handling Kit, plus some springs & pineapples).
Finally, larger wheels (17x7 will fit comfortably), decent rubber and anything visual (bodykit, wing, etc.).
If I've got anything wrong, or missed anything, feel free to correct me.