This game is not quite so big that it can't be played without references like most later RPGs. It does have several features that you might miss or be unprepared for, so a reference can be helpful. Where one draws the line is a matter of personal taste, of course, but I think I can say something a bit more helpful than that.
The only way that you'll get your characters up to high levels is to travel everywhere, do all the quests and kill everything. This means that you'll be exploring all the maps and will eventually stumble on all the special interactive objects. Telling you more about those would be an unnecessary spoiler.
You might want to know in advance that the storyline branches twice. You'll need to decide which path to follow and you'll want that decision to strengthen your team. If you want to avoid knowing more beforehand then it will be helpful for you if you can create characters that you will care about even if you want to choose a path later in the game that is not quite so advantageous for them.
Aside from that, you should probably be aware of the FAQs at TELP's MM7 website. We constructed them so that people could avoid spoilers and get only the answers they wanted. It was never totally finished but what's there is really good (if I do say so myself). Use the link below.