UK visit visa refused because of 'questionable deposits' [duplicate]

I personally would not appeal; as the decision to reject was valid based on the (lack of) evidence provided at the time of your application. An appeal is also not a straightforward, immediate process and has its own procedures.

You should have provided the source of your deposits initially when applying. It could be as simple as letter addressed to the embassy noting the date and amount of deposits and the source of income. It is even better if you could provide the requisite deposit slips or other information showing the source and nature of the funds.

Frankly, having an amount that is borrowed from a friend - especially if it is for the purpose of inflating your financial position in order to secure a visa (also called funds parking) is immediately a red flag and almost always guarantees a refusal.

I don't think the absence of a flight ticket hurt your application chances (you'll note, it was not mentioned as a reason for refusal either).