GBP/JPY is developing potential impulse subwave C (colored red in the chart), that is part of corrective wave 4 (colored royal blue in the chart).
The targets of the upmove are Fibonacci retracements of 137.03-130.26, and expansions off 130.26-133.16-130.74, 130.74-132.94-131.93.
Resistances:
- 133.27-29 = confluence area of contracted objective point (COP) and .382 retracement
- 133.64 = confluence area of objective point (OP) and .50 ret
- 134.13 = objective point (OP)
- 134.44 = .618 ret
If the price keeps declining the immediate supports will be Fibonacci retracements of 122.49-139.93, and expansions off 139.93-132.90-137.03, and also retracements of 130.74-132.94.
Supports:
- 131.84 = .50 ret
- 131.58 = .618 ret
- 130.00 = OP
- 129.15 = .618 ret

Overbought/Oversold
Assuming that the medium term trend is down but a corrective wave up is developing it's preferable to stand aside or try longs when the Detrended Oscillator gets below the zero level (current prices) or into the oversold area (30-40 pips below the current prices).
Read more on how to apply Fibonacci studies to calculate price targets.