Here's what I learned in short order:
Buy a shotgun that fits you and you will always like shooting it. Get a few different gauges and you're set for anything
New doesn't always mean better. Also, more expensive isn't ALWAYS better, but in general with guns, you get what you pay for (though some cheaper shotguns still do the job)
Buy good quality scopes from the start
As stated, buy the nice rifle you want from the start - the others will never mean as much
Everyone has their opinions - buy what you like, not what others say you should
Learn to work on every gun you own.