Originally posted by following.eric so tube and 50mm might be the cheaper starting point? at what aperture would I need to shoot or depends on how the images are turning out?
Very cheap, in the $10 range for the cheapest tubes. The aperture will depend on the images and magnification. Stopped down to f/4-f/8 is a good place to start. Higher will lead to diffraction softening things but might be worth it for more DoF (it depends on magnification and your tastes, so experiment!).
A reverse coupling macro ring would probably be the cheapest, these would let you mount your A-50/1.7 backwards onto your DA55-300 or the Sigma 17-50 (I have tried neither of these combos). Some experimentation is required to get a pairing of lenses that works nicely. Coupling rings are a few bucks, but you may need some step-up or step-down rings (also a few bucks each). Working distance (how far the front of your rig is from the subject) is typically close enough to be awkward.
My preference is still for the dedicated macro lens, 100mm being a good option. The 'budget' 100mm macros suggested above will all be terrific.
Originally posted by following.eric I want to avoid my 55-300mm as it's just not that sharp. I have to shoot at f13 to get acceptable sharp images and even yesterday in mid day light with clouds diffusing the light I still need over 1600iso to shoot at 1/400. I think the copy I have just isn't that great.
Ideally I love to be able to shoot at much lower iso so I can get cleaner images or more important more tack sharp images. I'll post a few examples if I get a chance.
Do post examples, and with flowers and other still things you should be using a tripod, mirror lock up etc. As magnification increases, with any method, the challenge of getting sharp and in focus images also increases. Using electronic flashes, tripods, reflectors, diffusers, etc. can all become handy pieces of kit to have available.