First trip to DLP! So exciting!! I remember how excited I was
Now the advice I'm going to give is not so much about specific rides, places to eat, etc but more about generally getting to most out of it so hopefully some of this will be good for you
Souvenirs - there is an abundance of shopping to be done and stalls everywhere. I have a rule that I browse only and then buy all my souvenirs on the second to last day (so I can pack it all ready for the day we leave). As I browse I have a memo set up on my phone listing the item, price and where I found it (as not all shops have everything and some items are area specific). Then I can make sure I use my spending money well to get the most out of it as the worst thing I could think of would be spending it all then finding something which I would rather have had instead of something already bought. Although, this is because we budget all our spending to avoid going overboard (as we easily would if we didn't budget
Water/Snacks - have a bottle of water handy to drink through the day and there's plenty of places to refill if you run out. Also have snacks as a little energy kick as the days can be tiring. Plus snacks can be expensive so it saves you some pennies to go towards souvenirs instead
Don't overuse the camera - Disney are great at hiding little details everywhere so try not to go mad with the camera and experience it with your own eyes. The best moment for this is on the day you arrive. That first walk into the park, onto Main Street and seeing the castle for the first time. Experience that first hand, not through a camera lens. Even though I have been to DLP a number of times I do this every time on the day we arrive. Obviously take plenty of photos if you want to, just don't get too caught up photographing every detail (trust me, there's too many to capture everything)
Enjoy the Scenery - Adding the last point, don't rush too much between rides (unless of course you are trying to get to a viewing for something at a specific time). There is so much to look at just by walking around that it's a good reason to take your time
Disney Railroad - Get on at Main Street and do a full lap of the park right back round to the Main Street station again. It's a great view of the park, you see it from a different perspective and there's a few little bits you will only be able to see while on the railroad. Its so pleasant as well so a good chance for a nice rest.
Disney Village - I personally dedicate half a day to explore the Disney Village. The shops are great and there's so much to look at. Plus I need plenty of time research so I can make sure I get the most of my spending money (see my first point
Lastly... Make sure you have comfy shoes!! And a lightweight waterproof in your bag doesn't hurt either.
Hope this information is useful for you and hope you enjoy yourself