Short answer: for gains of any kind you really don’t need to buy anything, your hands are all you need. A lot of products are junk or way overpriced almost junk contraptions.
Saying that, you can find good products at a good price to assist your PE journey (keyword assist). I bought a silicone sleeve ADS and I like it so far. Here is a in depth review of it that I made and hopefully should answer a lot of you questions ebay ADS review there are also links on that thread to other reviews of a stainless steel ball ADS that has worked well for some members. I am not sure if there really is a "best" product that I can link you too. While not all products are created equal, different ones seem to work differently for various individuals.
Monkeybars has a good reputation for selling quality products, but they are a bit pricey for my wallet. There is a thread on here somewhere about building your own silicone sleeves; I will see if I can did it up.
I like ADS over extenders(I think that is what you meant by stretchers) because a good ADS seems less restricting of circulation and easier to conceal. However, I have never used an extender and can not say for sure. Weights are better left alone until you can’t gain from other exercises. This is not just because it is one of the more dangerous forms of PE, many members believe gains come best when you do the bare minimum so that your penis does not adapt quickly to the strain put on it and stop growing.
Not sure how experienced you are, but why not just try the newbie routine for 6 weeks or so. Maybe you will be one of the few lucky ones who sees nice newb gains.
ADS (all day stretching) can be done for as long as one chooses to. Most would agree that any less than a couple of hours would be defeating the purpose of an ADS, but you should slowly build up the time and take constant massage breaks when first starting out to avoid injury and blisters.
Peace.