I've used quite a few peptides. I currently use Testosterone Cypionate for low testosterone due to methadone usage. T levels went from roughly 45ng/dl to +1,400ng/dl after a few weeks of injecting 200mg/week.
There are a few natural supplements that have been known to work; MACA, Ashwagandha, L-Citrulline.
Cabergoline has been reported to help shorten your refractory period significantly.
Cardarine helps with endurance.
Proviron is an AAS know for increasing libido, erection strength, and muscle hardness.
Vardenafil (Levitra) and Avanafil (Stendra) are both PDE5 inhibitors that are similar in effects to Sildenafil.
Peptides:
Melanotan-II is known for improving blood flow, which can help with erections.
PT-141 also improves erections, but has a short half-life, so it has to be used close to the time you want to perform.
DSIP helps regulate hormones, which can help with erectile issues.
Hope that helps.