I have some questions

1.I have a sister who wants to join but we pretty much have the same e-mail(the first name is different).Every time we sign up for a website where we can only have one account.Every one thinks I have a second account, then we both get banned.Is it allowed or could I get banned...or what?
2.How do I unlock party spaces.
3.How can I get scales besides nurturing egglings.
4.How much do custom mutations/hair/clothes/ect. usually cost?

You would only be banned if we thought both accounts were being used by the same person. And even then, we always notify the user(s) first and wait for a response/explanation. So in this case, you and your sister should be fine.

You can unlock party slots in the Plazas of Esior's Haven and the Sanctuary of Saerielle. You must first complete Jinxie's Capture Quest and open the reward from your Inventory before expanding your party though.

Scales are nurture only.

You can read about custom orders here: http://www.sylestia.com/forums/?thread=3638
You can view the custom order shop here: http://www.sylestia.com/shops/customordershop/#shop