A high quality mic will not automatically make your bank as popular or as well done as Gahata Meiji. There are several factors that lead to her success and even if you follow them, that's still not a guarantee.
1. Gahata Meiji is used as part of a marketing campaign for a brand of clothing.
2. With that use, she is also given a professional looking design as well as a well matching theme/concept that catches the eye.
3. She is recorded with a higher quality mic, yes, but she is also configured well - this is a huge (if not the largest) factor in quality. Even a low quality bank can be considered a pleasure to use when it is configured well.
Don't aim for being "UTAU famous" if all you plan on doing is recording a bank and doing little else. In the early days of UTAU that might have gotten you noticed, but the community is saturated right now (4,000+ and counting). Those who are "UTAU famous" contribute to the community in some form.
1. Sango makes well tuned covers.
2. Echoblossom, HaruVampire, etc. all make USTs.
3. Steel has his voicebanks, pvs, and artwork.
4. CZloid developed English UTAU for the overseas community.
5. Chasing Fireflies, KenjiB, and Plus/Minus amongst others make originals
...
In other words, they all do something that helps others and/or they do what they do with skill. It's simply not enough to do a voicebank and expect to instantaneously get noticed and if that's all you aspire for in UTAU, you're going to be left disappointed. Do UTAU because you enjoy it, not because you want to be popular.
As for getting a microphone that will increase your UTAU bank's quality, I can't give you a blind solution as I don't know the type of voice you have, but bodytemp has written a tutorial citing the differences between the type of mic you can buy (condenser vs dynamic) and a few suggestions.
http://utaforum.net/resources/microphones-what-is-better-for-me.126/
You can also ask her personally what mic would be best for your voice and where you can get cheaper alternatives or prices (look to spend at least $100 for the mic alone. you'll reach about $150 - $200+ for additional purchases: xlr cable, pop filter, shock mount/mic stand).
I personally have an sE Magneto as suggested by her. Results of this mic + well done oto: