I have tried a few, but far from an expert at lighting, .... far far away from that.
I bought into a few of the Fong gizmo's - have two of his Whale Tale thing-a-ma-gigs. They would fall under the "Why on earth did I buy that" category. Used them a few times. Now they just take up space. Lots of space.
I have a couple of cheap chinese ebay umbrella's. These I use. I should probably buy a quality one and see if you get what you pay for - if if the cheapies are just as good. Sometimes they are, often they are not. They are not durable but when I have used them, I've been happy with the results.
I have some cheap chinese slap onto your flash, soft boxes, small medium-small and medium (as in about 14"x10"). Actually the smallest one is used when I want to get away from the bright flash in my eye complaint. Works. Might look at some better ones of these things. The one I use the most is starting to fall apart. Fair mileage for something I probably paid $2 to buy.
I use the white diffuser that came with my SB-700 - it works for me - and it came with. Never use the coloured ones though. Tried once, na.
I have a nice bright LED light thing I picked up on eBay - not that cheap but good. I also bought some LED 'side" lights and flexible 'arms" to hold the lights on either side of subject in close up photography. Good for shooting small items where you want good control of the lighting. A bother to fiddle with though. The big bright one recharges internal battery or runs plugged in. The small ones use AA's which is OK. But they are not that bright. Bought those retail.
I have one of those pop open reflectors , use if infrequently. At least it stows away easily in its bag. Mine is about 3' diameter White one side gold on the other.
I have played around with Nikons CLS with two flashes, plus my pop-up (which I have one of those pop up cover over diffuser snap-on things). I add that bright LED sometimes bounced off of my reflector (it does get some use).
What I know is that I don't know much about lighting - and I know that knowing how to use light would be a very good thing. I've read a bit about lighting and it is something on my "I should spend some time learning more about this" list.
I like to shoot small models ( no not short people who pose but toy trains and other models of that kind). I've read about light boxes and tents, have used a opaque white storage tote with bright lights shining through - didn't get the effect I wanted. Might build me one of the DIY lighting tents to shoot stuff .... also on my 'someday' list.
I hope people who know what they are doing will chime in and give you some helpful advice.