Hi everyone!
I have never really been into keeping pet fish, since every single gold fish that I have kept as a child has died overnight. My parents would not give me money for them either so I've never really had any pets. But my friend has recently gone on a vacation and she needed me to watch her pet Betta for her. I've kept it on my desk and this little guy's been growing on me. So I decided that I want to get some of my own! :)
So I've been doing some research here and there and I still have some questions. I want more than just one fish in my tank and I thought about some of my options and read that I could keep female bettas together.
I want to get 3 female bettas, and I want to get something like this

Can someone show me the differences (with pictures) between a male and a female betta so I dont accidently buy 3 males and send them to their deaths?
How big of a tank should I get? I was thinking maybe a 10 gallon tank. Are there any reliable name brands that I should look for? I dont want to buy a tank that'll be defective or break on me somewhere down the line. What would be the price range for these tanks?
How do I keep the fish together? I will use dividers if necessary but I want to avoid that. How do I go about introducing the betta into the tank?
What kind of accessories will I need? A filter and heater mainly from what I've learned. Is there anything else? What kind of surroundings should I put them in? Should I use sand topped with rocks or just pebbles or sparkly marbles? Ideas for plants? What about lighting? What colors do they prefer? Anything else I need to know before I take off on this adventure? Thanks for your help!