Hi,
Do not buy those eBay tubes. They are the very cheap ones already mentioned that don't have the electronic contacts for AF or aperture control. Next to useless and pretty much a waste of money.
Brand new, a Kenko tube set at $160 US is a better choice. It's got three lengths of tube in the set - 12mm, 20mm and 36mm. A set like this gives you seven possible combinations to experiment with. Canon only sells individual tubes: a 12mm for about $100 US and a 25mm for about $130 US.
You might want to get just the macro lens first and try it without extension tubes. But, I can tell at a glance that unless it was cropped down from a larger images the particular shot of the bee you show would have needed more extension, even with a 1:1-capable 100mm macro lens (all the ones you listed are 1:1 capable... except for the much older Tamron 90/2.8 manual focus lens, current models will go to 1:1) on a crop sensor camera body. Tubes can be used with many different lenses, to give closer focus, near macro and higher macro magnifications. Experiment with them. I never leave home without at least one set in my camera bag and have used them with every camera system I've owned over the past 20 or 25 years.
You will likely also want a flash. This is to offset the fact that you will very often need small apertures to get adequate depth of field, which can get razor thin at higher magnifications. Smaller apertures mean slower shutter speeds... to off set that you use a tripod and/or a flash.
The camera's built-in flash is not at all useful for macro, and really not for much of anything else either.
It doesn't have to be an expensive, macro specific flash. I have a modified Canon Macro Twinlite, but often find myself without it and just using a single 550EX handheld off to the side and slightly above, controlled via an off camera shoe cord. Any 580/550, 420/430 or even 220EX (although the latter is too "auto only" for my tastes) would do well too.
At macro distances, all these flashes are sort of like a massive softbox in relation to your subject, so a single flash works surprisingly well and wraps around your subject without casting heavy shadows like you might expect. The biggest concern is that the flash over-powers the subject, is too strong even at it's minimum output. To counter that, a simple trick it to buy a roll of white gauze (bandage, without any adhesives) from a pharmacy. Wrap a layer or two of it over the flash head and use a rubber band to secure it in place. That reduces the flash's output very effectively and you can add or subtract layers to change it, as necessary.
I dislike the flat lighting that a ringlight gives, so I seldom use one. Some people love em. Oh well, different strokes...
I have and use the Canon 100/2.8 Macro... current version with USM that makes it more useful as a dual purpose lens, as a short tele at non-macro distances. The older version focused slower, which doesn't matter at macro distances but can be a big difference at non-macro distances.
I've also got a couple of the Tamron 90mm in other camera systems. Good lenses I've used for a number of years.
I've not used the 105 Sigma, but it's said to be pretty good.
I think you are on the right track, with a macro lens in the 90mm to 105mm focal length. Any longer is too difficult to hold on a 1.6X crop sensor camera like the one you're buying (my Canon 180 Macro is a wonderful lens that saw a lot of use on my EOS3s, but is not used much on my crop sensor digital cameras). A longer macro lens like a 150 to 200mm means a lot more tripod work.
Any shorter macro lens and you can find yourself too close to your subject, which is a consideration when shooting anything that stings or bites or gets scared away easily... and risks casting a shadow over the subject.
Speaking of which, one other thing that's very handy to have is a diffuser/reflector. Subjects out in bright sun are just too contrasty, if you are shooting with available light. I use one example, a Photoflex Multidisk
in various diameters. These are made by various manufacturers, fold to store compactly, and each have a diffuser and several different reflectors from which to choose. Handhold the diffuser panel over a sunlit subject, to manage and reduce contrast. Or, use the reflector to bounce available light onto a shadowed subject, or to compliment what you are doing with a flash.
There are some great books about macro shooting techniques by some real masters. It's a detailed subject and those books will give you many more ideas, suggestions and tips than we can possibly cover here. John Shaw's "Close-Ups in Nature" and Tim Fitzharris' "Sierra Club Guide to Close-Up Photography in Nature" are two good ones that come to mind.
For example, among other things they'll explain why you will find auto focus of little use at macro magnifications, and tell you how to focus moving the entire camera and lens back and forth (the focus ring acts almost like a zoom ring at high magnifications). This is a tripod technique, with a geared focusing stage, or a long lens plate, or on a monopod, or even completely handheld or lying with your camera sitting directly on the ground or any other solid surface.
Have fun!