BMX parts: first upgrades worth making

1. Platform pedals (nylon or alloy) with good pins: more grip and control.
2. Tyres suited to your terrain (smooth and wide for street/park, narrow for racing).
3. Grips that feel good, with bar ends.
4. Pegs if you grind (nylon/plastic sleeves for skateparks).
5. Rear hub with sealed bearings and, later, a freecoaster if you want to ride backwards.
6. A quality chain with well-aligned sprocket and driver.

Buy compatible parts: axle sizes (rear is usually 14 mm, front 10 mm or 3/8"; check your bike), bottom bracket type (Mid/Spanish/American) and tyre width.