I did El Nido cheap and it was still one of the best weeks of my life. Tour A (the lagoons) and Tour C (the hidden beaches and Matinloc Shrine) are the two to do — I skipped B and D and didn't feel I missed much.
Stay in town and walk to the joiner-tour offices the evening before to compare prices. A dorm bed, street barbecue dinners and shared boats kept costs way down. Pro tip: go to Las Cabanas beach for sunset, it's free and unreal.