This is actually a fairly common question and not one that is often addressed adequately. the following is the, slightly edited text of a reply sent by Howard Rogers www.dizwell.com to someone who asked this exact question. the post is so good, that with Howard's permission I reproduce it here. the 'where' referred to below is the Usenet Group Comp. databases. oracle. server which can be reached via the link on the left or via your favorite newsreader.
Be patient. you're starting from scratch, so there's a lot to learn, and much of it may seem very strange to begin. visit the online documentation set to get access to the latest Oracle documentation (though your CD set will probably include it already ). read the official concepts guide. then visit sites such as that maintained by Jonathan Lewis, and ask Tom. visit Google and hunt around for advice. take nothing on face value: Test it yourself to destruction. lurk here for a month or two, and try and pick up on the sort of questions being asked, and ask yourself how * you * wowould answer them. then see what answers actually come through, and compare. when you're feeling brave, post some of your answers and see how they are taken by people.
Buy books. anything with the names Jonathan Lewis, or Thomas Kyte on the cover are * extremely * Good bets for accurate advice. O 'Reilly are good. as are apress (used to be wrox) avoid anything that mentions OCP (Oracle certified professional ). the qualification is not worth a damn, and leads you straight into myth territory.
If you can afford an oracle Training Course (most people can't), go. go to DBA fundamantals I if you can... the architecture stuff they cover on that is extremely good (but you play Russian roulette with the uctor you get. if the guy starts reading from the course notes in the first hour, then leave and ask to be scheduled with someone else at a later date ). DBA fundamentals II is quite good, but is light on networking, and the backup and recovery stuff is not difficult. don't bother with performance tuning, because it's a badly-written course that addresses none of the real issues. I think the general thing is to get involved and to get communicating, and you 've already started that by posting here. just don't stop now.
The other general thing is to test and test, and verify for yourself. experiment, and stuff the consequences. the other thing I wocould suggest, given your background, is that you learn oracle at the command line, and learn * Oracle *. worry about putting a graphical front-end app. on top of Oracle later. when you 've got command-line Oracle sorted, the graphical front-ends will come as second nature, and will be better for the understanding you have of the back-end architecture and inner-workings.
And finally, enjoy yourself. oracle is quite a majestic system. it's got an internal logic that is beautiful, and the sense of power that you can get from controlling those internal workings can be quite exhilerating. so have fun.