There are two major issues about the ordering of crisps.
Issue 1: In which order, or orders, should one attempt crisps of various flavours?
Issue 2: Forced into a situation in which one is to eat both crisps and chocolate, should one eat the crisps first and then the chocolate, or the chocolate first and then the crisps?
With respect to issue 1, I think the only good answer is that it depends. The traditional answer would be: prawn cocktail, followed by one of the savouries (beef, chicken, bacon), followed by cheese (and e.g. onion). But one may have been been presented with a non-traditional range of flavours. And even presented with the traditional selection, there are dissenters from the traditional scheme.
Issue 2 is, again, a source of dispute. In part, individual responses will depend on individual taste: a matter of whether an individual would prefer the crisps, or rather the chocolate, to be enjoyed without contamination. However, there is presumably a fact of the matter here, albeit one that is hard to fathom. It may be that the answer is in part empirical, though we are not yet in a position to describe the crucial experiments.
I haven’t here attempted to decide either issue. I hope to have at least made plain what the issues are, to the extent that we may begin to attempt their resolution.