So, what do you have (in terms of money) and what is your playstyle?
Edit: the problem here is that there's a large gap between the Keelback (or the Asp Explorer) and the Kraits/Python in terms of money. The Keelback comes in at 4 MCr. naked, the Kraits/Python at ten times that amount (and that gap doesn't get better if you include outfitting them...). Anything inbetween is either superpower rank locked (Federal shoeboxes, Clipper) or strictly designed as short-range combat ship (Alliance).
The one exception is the Type-7, which makes a worse miner than the Keelback - sure, more cargo space, but she needs a large pad and can only carry 4 small guns.
Easiest way to get a couple of hundred MCr. would be either "Road to Riches", or maybe
@CMDRQuainMarln 's proposal of a heavy metal mining weekend on his carrier.