It's imposible to answer these questions catagorically, without a detailed understanding of the OPs circumstances, location and diving goals.
Loyalty to your LDS is to be applauded and encouraged. However, don't rule out the huge second-hand scuba market on craigslist and ebay. With diligence and patience, it could be possible to get all 3 items (BCD, Regs and Computer) for $500.
Here's my list:
1) Computer. Often unavailable, or overly expensive, to rent. Lightweight and easy to take away on holiday. Aids safety and encourages independance from the 'sheep' mentality of following a divemaster or more experienced buddy. Develops understanding of time/depth and nitrogen absorbtion. Helps in the event of emergency decompression situations. SUBSTANTIALLY LONGER DIVE TIMES! No later requirement to buy a depth gauge for your regulator set.
2) Regulator. Safety and security of having your own (well maintained) regulators. Own purchases are likely (hopefully) to be of better specification than average rental regulators. Can customize mouthpieces for better comfort.
3) BCD. Rentals can sometimes be threadbare, uncomfortable and/or a poor fit. Having your own BCD ensures comfort and quality of the BCD. Own purchases are likely (hopefully) to be of better specification and condition than most rental BCDs. Definitely consider a Backplate & Wing (BP&W) design BCD. There are many threads here dealing with jacket vs BP&W bcds.
4) Wet/Drysuit. Little point investing in a wet/drysuit that will not be practical in different environments, if you are travelling around to dive. Wetsuit rental is cheap in holiday destinations. The heaviest and bulkiest item to travel with.
Just for your interest, there is another simular currently active thread
(BCD, Regulator, or Computer?) that may also aid you.