E-commerce solution

I have been setting up a store using shopify and have come across a few hurdles including payment gateways and slight design issues. It hasn't been launched yet and I want to get advice and edits done from someone who has knowledge in this department. I'm not adverse to using a different platform if existing product uploads can be transferred. Ideally I'd like to use paypal alongside elavon with 3d secure.
Please get in touch with any questions. The budget is just a guide.
I'm wanting to launch in the next week.
Thanks