Ireland's student visa is applied for online and then supported by a documentary file submitted to the visa office. The programme must be an eligible full-time course, the fees must be paid or substantially paid, and the funds must be evidenced.
What distinguishes Irish decisions is how explicitly the reasons for refusal are stated. Files are refused for insufficient documentation, for finances that do not demonstrate capacity, and notably for an unconvincing account of why the course is being taken at all.
Fees paid before the decision
Ireland expects tuition to be paid before the visa is decided in most cases, which puts real money at risk ahead of an uncertain outcome. Institutions generally operate refund policies for visa refusal, and you should read that policy before you transfer rather than after.
This ordering is also why a weak file is expensive in Ireland specifically. The cost of a refusal is not only the intake.
The finances
You will need to show funds available for living costs for the year, plus evidence that the same level of support can continue for subsequent years of a multi-year programme. Sponsor-funded applications require the sponsor's own evidence, the relationship documented, and a plausible explanation of the source of the funds.
Recently deposited lump sums are read exactly as they are read everywhere else. History matters more than balance.
The study rationale
Write the statement as an argument, not a biography. It should explain what you have studied, why this specific course follows from it, why Ireland, what it costs, how it is funded, and what you intend to do afterwards. Each of those should be consistent with a document elsewhere in the file.
Where there is a gap in your timeline, account for it plainly. An unexplained year invites the reader to supply an explanation of their own, and the invented one is never generous.