A few points.
First, take lessons and work your way up to doing a circumnavigation. This takes a lot of time and preparation of the sailors involved. Many recent circumnavigation attempts failed because the sailors involved did not prepare themselves properly. Start by daysailing, then coastal cruising, then short bluewater passages... and sail in as much bad weather as you can. Sailing on a nice sunny day with 10-15 knots of wind isn't usually the problem... sailing on a day when it is raining horizontally, with the wind blowing like snot, 25-30 knots and gusting up past 40... are the days that will really kick your butt. However, you'll want to work your way up to the really snotty days.
Second, get the boat you're going to make the passage on sooner rather than later. You'll want to get as familiar with the boat as you can. Knowing the systems intimately may save your life. Also, you'll probably want to modify the boat to suite your needs. I'd recommend you look at James Baldwin's Boat List
as it has a number of relatively inexpensive pocket cruising boats that are bluewater capable. I'd also recommend you read the Boat Inspection Trip Tips
thread I started, as it will help you determine whether some boats you look at are even worth going forward on, saving you the price of a survey on boats that aren't worth looking at further.
Third, save at least 20-25% of your budget for modifying, refitting and upgrading the boat you buy. Chances are likely that any boat you get will need some modification and work done to it to make it suitable for a bluewater passagemaker.
Fourth, getting a job in the marine industry is a good idea. It may give you a line on boats for sale, as well as experience in doing repairs and maintenance. You'll need skills in electrical, mechanical, plumbing, fiberglass, rigging, and electronics at a minimum. The more skills at repairing and maintaining the boat you have, the more likely you will be to succeed.
I'd point out that getting a boat ready for a bluewater passage is not generally an inexpensive endeavor. Nor it is one that can be done for just any boat. It will also probably cost you more than your meager budget... at a minimum, it'll be 13k rather than 5k.