If you look in this forum section you can find extensive discussions. Right now the US portions (including Puerto Rico) are free in BSB
chart formats. You can purchase BSB charts
for the islands.
There are a host of computer software
based charting systems that will allow you to connect a GPS
and that represents a good value if you think you want a computer on board. If you want a chart plotter then the formats are proprietary to the plotter manufacturer and the charts may cost a bit more.
Having a system you can use is worth more than the differences in cost. I would also strongly suggest you invest in at least the chart books
in the large formats as a paper backup to save some money
. You really need good charts. It's not an optional item. Cruising guides
are also quite valuable and there are many to choose from.
Wade through the existing threads using the search tool There really is everything you could want discussed already.