- How much r u willing to spend? ---> close up or extension tubes are the cheapest route. 
- What kind of pictures r u interested to take? ---> may determine your interested focal length or DOF that u r looking for.
- What lens do u alrdy have?   ---> potentially just add close up lens or extension tubes.
- Ready/Willing to use tripods when doing macro shots? ---> VR may help you if u want to do handheld shots.
- If go by macro lens, willing to use manual or do u want auto focus? ---> I'm using tamron SP AF 90 (no VR lens) and sometimes pair with Raynox & tripod ... I do try them with extension tubes too (macro+ET+raynox). But I don't have nice pics to share.. hehe. I'm noob.

There r many options out there. Macro lens, close up lens like raynox or others, extension tubes or ... a combination of these three for a supper macro works! hehe
I'm also a newbie ...

pic spam :

Which one looks nice/appealing to you guys eh?
Was playing around with single light source, editing and tones/colors.
**All shot with D3100 + Tamron SP AF 90
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I have another two pics if you are willing to look at them too.


Thanks!