A lot of explosives are surprisingly easy to make. The challenging part is not blowing yourself up in the process.
Talking about things that go kaboom reminds me of a test I was briefly involved with. One of the federal agencies wanted to conduct some tests on a specific type of explosion, an air / fuel explosion where a fuel was dispersed into the air and then ignited. The problem with trying to blow up a large amount of fuel, like in a gas tanker, is the AFR required. If you want to blow up a soda litre with fuel for example, you'd really only need to put a splash of fuel in it, let the gas fumes fill the air and then ignite it with a blasting cap. If you were to fill the litre with gas and try to ignite it, chances are you'd just end up setting the fuel on fire for a short amount of time. So this test used two explosives, one to disperse the fuel and the second to then ignite it. It was very difficult to get it to work and unreliable but one time, we had a water tanker that is normally used on a construction site, with 2400 gallons of a certain fuel. When the fuel was blown up, the energy from the blast shook the whole town. I went later that day to a store about 6 miles away from the site where the blast happened, and the blast blew the doors wide open. From the site to the store, there is a mountain in between them. Most of the shots done at that company don't effect the town, due to having a mountain between the test range and the small town.
This test completely obliterated the tanker. I found half of an end cap of the tank, about 100 pounds of steel, roughly 400-500 yards away from where the tanker used to be. We couldn't find the cab of the truck. Had we used nitro as the fuel... we probably would have destroyed millions of dollars worth of windows. Nitro is sometimes used in shape charges, for example.
ANFO is an amazingly simple and stable explosive with a rather impressive amount of energy. It's actually classified as a blasting agent, lol. If you really want to play with something "safe", ANFO would be on that list. You cannot make it with regular fertilizer anymore I believe, pretty sure they now have to mix in a chemical to make it unusable for ANFO.