Oi vey, darling, there's so much more you need to know then just that.
+Goldfish don't eat other fish (or atleast mine haven't, and that goes for pets as well as the smaller ones for feeding my turtle). They produce high waste levels, which isn't good for a general community tank, which is why in most pet stores, they're kept in seperate tanks.
+Nearly all fish will eat another dead fish though. I've even seen plecos (suckerfish--algae eaters) do it.
+Most fish do eat the babies. To avoid this, if you know your fish is pregnant, you put her in a birthing tank, and it'll keep them seperated from the mother, so they can be raised safetly.
+Most pet stores have markings on the tags of fish that show how aggressive they are, so you never wanna put an aggressive fish (like a cichlid) with something more peaceful (like an angelfish). That would be the best thing to do, actually. Go down to the petstore, look at the fish you like, and talk to the person in the fish department about that. Make sure you thoroughly discuss what living conditions it'll need as well.
+Since I get the feeling you're a newb to fishkeeping, you need to know that there's more to it then dumping water in a tank. You'll need water conditioner, to declorinate the water, and most (I use Kordon Amquel+ and NovAqua) remove more harmful things from the water, and add beneficial things to it. Despite being freshwater, it's also a good idea to get something called Aquarium Salt..it enriches the water, and can be used as a general medicine. It's also vital you get a test kit to constantly test the water (API makes excellent test kits), the strips don't really do a good job. While airpumps aren't neccessary, they're nice to add oxygen to the tank. Make sure you get a filter adequate for the tank, it's actually better to get one slightly bigger than the actual tank (I have a filter good for 75 gallons in my 30 gallon tank, for example..you don't have to be that drastic, but it's a good idea.)
+Also, pleco's don't mean the tank stays clean and you never have to do anything. There's a fine difference between algae and fish waste, and the pleco also being a fish, consuming things, it's also producing it's own waste. They also don't eat all kinds of algae, so even if your tank gets algae, that doesn't mean that's what it needs. It's always a good idea to supplement their diet with algae wafers. Also, depending on the size of your tank, don't get the "common plecos" you see in the pet stores..they get too big for most tanks, so make sure you get something that stays smaller, such as the clown pleco. Again, research online or talk to an expert about the right fish for your setup.
I have a 75 gallon freshwater tank with 5 gouramis, and with them are a rhino pleco, a channel catfish (don't get one of those unless you have the capability to properly care to an adult, which attains up to 4 feet), and a bichir. I think a secret is that I keep plenty of ghost shrimp, mollies, and guppies to keep the carnivores preoccupied as opposed to the larger fish. Having such ample space also helps deflect conflict. I tried keeping bloodfin tetras and hatchets in there as pets, but they eventually disappeared, so if keeping something like a crayfish, catfish, or bichir (commonly called dinosaur eels), you should be sure you have larger fish with them.
Anyway, I believe I covered the basics. Once you know what fish you're getting, make sure your tank will be ample for them, make sure it's decorated right, that you have a heater to keep it at the right temperature, good lighting, a great filter, and that the levels are right (such as ph, ammonia, nitites, nitrates, etc).
Oh, water changes will be neccessary no matter what, so a gravel vac and a bucket will be a good idea, depending on your budget, a python no-spill clean and fill is a fantastic investment, you can get them much cheaper online than in the stores, though.
But you asked about fish, so having prepped you, I'll be happy to tell you:
Angelfish, Barbs, Cichlids (they can be kept with each other), gouramis, rainbow fish, and discus.