I lusted over the pink tower and broad stairs for years, but never got it. We did get a set of large stacking blocks, which are similar -- but without the mathematical ratios of the pink tower that makes it so cool. It was enough for us, though.
What I did get:
Knobbed cylinders (full set of 4, but only the mini ones with 5 each instead of 10) -- love these, DD still plays with them at almost 5yo.
Number rods (the alternating red/blue ones in lengths from 1-10) -- love these too, but didn't use them much, really.
Wooden place value cards -- absolutely fantastic. We use RightStart math now, and instead of the cheap plastic cards you can get from them, the wooden ones have been really pleasing to use. These get used a LOT.
Hundreds tiles -- here you have choices, the more expensive (but very conceptually clear) squares of 100 connected beads, or the cheaper solid wooden tiles with 100 markings on them. We went for a set (comes with 45) of cheaper tiles. RightStart uses simple folded paper 100's tiles -- we like having the solid ones to work with.
Beads, bead bars -- I ended up buying some wooden beads and making my own 2-colour bead bars, based on the RightStart methodology of 5+x for numbers up to 10. These are essentially the same as the bead bars you get for the 'snake game'. There are lots of options for bead bars, though, and they all have benefits and uses.
Metal insets -- Haven't used these as much as I thought I would, but now that she's getting a bit older and starting to write more, we might pull them out again. Love the concept.
I keep thinking about getting some 1000 cubes, and I actually probably will soon. I just keep debating over whether to get just one but have it the actual 1000 beads, to REALLY demonstrate the idea of 1000 'things'... or to get a set of 9 of the solid wooden cubes, to use in trading/addition manipulations.
I also never got any sandpaper letters, tried making some at one point but abandoned the project. I *did* end up making some movable alphabet letters of a sort, though -- big puffy scrapbook letter stickers on craft foam rectangles. Purpose of those is for making words and sentences without having to 'write'.
I also made a homemade version of colour-matching tiles, just with clothespins and paint sample cards!
I got a nice wooden shape-matching block (the type with the shapes you push through the matching holes), and made shadow cards by tracing the shapes and writing the name of the shapes. She LOVED that activity.
I didn't get into and Montessori math materials beyond what I've described here, since I knew we'd be using RightStart (which is Montessori-BASED but not 'pure') once she was beyond 'preschool' math stuff. So, no binomial cubes or multiplication boards (though those are really, really cool heh).
Other Montessori stuff we did, didn't need any special tools -- tweezers, spoons, cups, etc, for pouring and transferring activities. Didn't bother with dressing boards, we just practiced with real clothes. Many Montessori objects of that sort are intended as idealized replicas of what would be in a home, for the purpose of school -- but if you're homeschooling you might as well just use the real home objects!
As for figuring out what to do with the stuff -- you don't need Montessori training. :) But it can be VERY helpful to read up on some of the lessons and techniques. Knowing not to interfere when your kid is working at an activity, for instance! (and why!) There are TONS of homeschooling Montessori mom blogs. There are even websites with the actual Montessori manuals for FREE. There are books like "Teach Me to Do It Myself", and "Montessori in the Home". Even Montessori's own books -- which are more about the ideas behind the method rather than the practical usage of the materials, in general -- are quite enlightening. :)