I've done a ton of macro work freehand. More fun that way IMO. In all honesty the high end Gorilla Pod is pretty stable and something I keep with me everywhere. With a low end 55 lens (very light weight generally), you can get away with a cheap tripod. I would look for a 3 way video pan head/kit off Craigslist or eBay and pick up a set of cheap (heavy) legs if you're really worried about it.
This is just me, but I would upgrade the glass first. That's dependent on how much you want to spend of course. Extension tubes are a GREAT addition to any kit and really a load of fun to play with. However if you were to upgrade to a true macro lens and shoot at 2.8, you wouldn't have to worry about lowering your shutter and picking up more blur nearly as much to make up for the stop difference of the tubes.
I'm not sure how many or what size tubes you'd be using of course, but you're looking at a 2 stop shift to use a mid tier tube, and you're already at 3.5. Oh, plus if you do upgrade the lens instead, you won't really need to buy floods either. A well placed flashlight provides plenty of light for smaller objects at 2.8; you can build light boxes super cheap too.
As an aside, being the internet, I don't want any of this to come off as condescending or taken the wrong way. Just wanted to add my two cents.