I agree with what Donya said, except I've never had a Bernina. If you search the internet for customer reviews you can read what experiences others have had with various machines. A really good site is patternreview.com where you can find tons of reviews. I've read good things about Kenmore on that site. Don't think you have to get all the fancy stuff, just a reliable machine like Kenmore, Viking, Pfaff, janome. I would think that it would be more important to develop your skills in construction, design, draping, fit, etc than knowing how to use all the bells and whistles on a fancy machine (like decorative stitches of hearts and flowers, etc). It doesn't take a fancy machine for a creative designer to express her talent. Make sure lots of different feet are available for the machine so you can learn different techniques that are really hard without the special feet. Definitely don't get into all the embroidery machines. Babylock sergers are good, I've heard, but again, you don't really have to have one to start learning design and construction.
Hope this helps. Good luck to you.