I understand the temptation to start off with buying a populated account, as you assume that the methods you've read up in will pay dividends.
However before buying an account, have you just tried to grow one in your niche and monetise that yet?
I think you should consider browsing the marketplace for Instagram accounts before you risk $ on Ebay.
Here's a filtered marketplace search for "Instagram" https://www.blackhatworld.com/search/19679993/?q=Instagram&o=relevance&c[title_only]=1&c[node]=200
I already tried but it takes too long. the idea is to buy an account and monetize it. This is my preferred account.
What's the cost? Compare that to other sites such as Fame Swap, which will be hard as they don't have low accounts with only 2k followers.