For serrapeptase, I've been taking Doctor's Best which recommends 1 capsule / day on an empty stomach with water. I think I mentioned before, but be careful if combining with pain relievers and anti-inflammatories. Serrapeptase will thin your blood a bit, so combined with aspirin can cause low blood pressure and dizziness. It shows a lot of the same benefits as aspirin though, so you may find it to be a better option anyway with less impact on your stomach. I'm continuing to take this daily as the potential negatives seem low. More info here.

I've also been skeptical on supplements in general, but given the injuries over the past 3 years and the fact that I'm now 34, I'm trying to get any advantage I can to recover from workouts and continue performing at as high a level as possible for as long as possible. Other supplements I've been taking:

• Daily multivitamin
• Fish oil
• Kelp — helps regulate your thyroid and hormone production related to metabolism. Careful not to take more than 225 mcg/day or it can actually be detrimental. Probably only suitable for folks who are working out / training consistently for these reasons. I use Swanson brand which is right at 225 mcg in one daily tablet.
• Acetyl L-carnitine which supports energy, brain function, and metabolism. I use NaturaLife Labs, 2 tablets/day.
• CherryActive Capsules — freeze dried cherry tablets which many pro footballers use as a nutritional supplement and that can also improve energy levels.

Good luck!