I'll try to add other tips as I think of them. For example, besides ways of making money (neopoints, or NP for short) you should also know ways of saving money.
When you get a food item, such as from a daily or random event, check its value first. Some can be worth hundreds, or even thousands, each. It's your choice, but if I was just starting out, I wouldn't feed something that expensive to my pets, especially when there are free food options that will satisfy them. The Giant Omelette and the Free Jelly links are on the Dailies page. Clicking on those sends the food item to your inventory, where you can feed it to your pets. That's how I keep mine fed, as well as from the Movie Central link. That one doesn't actually send you food. For that, once the graphics load, you click on the left door and go inside to the theater concessions area. You can choose from one of the food items (such as popcorn or burgers) and click each for all of your pets. The fed pet on the right will then appear blurred out some until the next day when you can feed them again there. I keep pricier food items in my Safety Deposit Box or sell them.
Another choice you'll have is whether to accept Faerie Quests as they show up (search the topic in the Index). These quests will increase your Pet's battle stats, depending on which Faerie you see. You don't have to accept, especially if you are low on NP, or don't care if that pet's stats go up that day. I keep a separate browser window open with the Shop Wizard so I can check the cost of the item the Faerie asks for before deciding if it's worth accepting. If you don't already have the Wizard page open, it won't let you use it while you have a Quest underway, so plan ahead for that. (There are Faerie help threads in this Forum if you forget).
http://thedailyneopets.com/articles/faerie-quests
This last tip for now isn't about money. I keep several low value toys in my inventory and play with my pets almost daily. I'd rather see the happy looks on their faces :wub_anim: than the frowns :sad02: that will show up when they get ignored.