Not a beginner, Capital isn't a problem, I run a crypto based business and am always looking for sources to buy large amounts of coin at good rates.
I'd say probably Localbitcoins[1], as you wouldn't have problems with banks and taxes and stuff because you can purchase peer to peer, even with physical cash. Though I'm not sure if you can call it "good rates" though. I suggest posting your own offer for optimal rates.
[1]
https://localbitcoins.com/