I've read a few of the posts and totally agree. Social media. Social media. SOCIAL MEDIA. You CANNOT overdo social media. Plus, it's FREE!! Now that you've got something on FB, set up a twitter account. You can connect your FB to Twitter and it will automatically post on your behalf. But you will need to do the appropriate hashtags on separate posts too in order to gain followers. Follow dog lovers and have others follow you.
Instagram and Pinterest everything you do. Again, use appropriate hashtags on IG.
On ANYTHING and EVERYTHING (business cards, handouts, flyers, ads, etc) that you print out, you need to have a QR code leading back to your main business page (sounds like FB), along with your Twitter, IG, etc handles. I use qrstuff.com to generate them when I need it (free).
Most importantly though, scout threads and give people what they want. There are SO MANY similar designs out there so make sure that yours really are different. Get feedback and suggestions and don't take them personally if there is any criticism.
Go to local boutiques and groomers and show them clothes you have already made (shows quality). Keep a portfolio and show managers/owners other designs (shows variety).
If you have enough stock, go to shows (crafts, dog, pet, flea, etc). Always carry your business cards (hand them out to owners whose dogs are wearing clothes) and have an elevator speech ready.
Basically, pimp yourself out and have patience and persistence. 