Some photos of your new home will help with advice for you. How exciting!!!

if you go with the most trendy things.. you will find there are lots of knock off's and clearance items that match.
If you do furniture in natural colors and accents in bright colors you can easily change your color scheme if you decide you want something else in the future.
Make sure your small decorative items are cheap.. You can find throw pillows that are $7.00 and you can find throw pillows that are $100.00.. go with the $7.00 ones...
Find items that can be used for multi purposes so they can be interchanged to other rooms in the future.
A fold leaf table could be a buffet or craft table later on.
Bedroom furniture can get passed down to kids or made into guest bedroom furniture.
Small dining tables can be made into office desks etc.
If I had it to do over again.. I would have done a cute folding table and chairs for my dining table and when I got my big house retire those items to storage and brought out for out door parties.

Have you identified your style yet? If so the houzz ideabooks have a lot of articles that are helpful (such as "your style is cottage" etc).
Also start ideabooks and browse the photos for inspiration to see some common themes of what you like.
Target and ikea are great for budget friendly trendy and modern items. I also like Marshall's and home goods for pillows and accessories and sometimes furniture and rugs.

Congrats! I just bought for the first time, too. At least with the walls, my approach has been to start with the room that has the most limitations (windows, doorways, awkward spaces, etc.) because the space sort of narrows the options for you. The walls with no broken up space are super overwhelming, but I think it's okay to leave them bare for a while as you decide what you really want/like. (So far I only have things hung in the kitchen, bathroom and above a fireplace.) I like to let the space narrow my options for me, i.e. use a warmer blue for the walls if your wood floors have warm undertones. A good article on colors depending on your lighting: http://us.farrow-ball.com/how-light-affects-colour/content/fcp-content. Not sure about your situation, but a lot of my furniture is hand-me-downs and not update-able in the near future so I stick to changing pillows and throws. If you are buying furniture, I recommend getting a solid colored couch and saving patterns for your armchairs or pillows, which are more easily (and inexpensively) updated.