You'll feel like shit and get locked up. Also your family will see you as crazy for the rest of your life.
This is absolute worst case scenario. It's not the same for everyone.
I never tried to commit suicide. But i did some stuff close to suicide. I have the weird anxiety that if i survive a suicide attempt i see this as a wonder, Like a miracle and gift that i should live on. Moreover i think this is a very scary and brutal event. My big hope is that i succeed the first time if i try. Therefore i would try to combine two methods. I am really scared about surviving. The feeling must be shitty and I fear the damage that can occur.
What is your experience?
Obviously, you'll keep living. What happens after depends on a lot of things.
If you are found and saved, there's a possibility you will end up sectioned and admitted into a psych ward. You could be referred for meds and therapy.
If nobody knows you tried, that's probably not going to happen.
People might become aware of how you're feeling, but it's not guaranteed to be all bad. You might find support and real help. It all depends on your relationship and how understanding they are.
Depending on your method, you might suffer lasting damage or just feel sick for awhile after and recover. It all depends. Some methods are riskier than others.
I totally understand the anxiety about not getting it right, but I'd recommend against more than one method. Just pick one, keep it simple, and do it right. When you start combining methods, it really just creates more things that could go wrong and make you fail. It's generally overkill.