I have read your requirement about creating an online store for your T-shirt and Accessories Business. I have listed some basic functionalities I have understand from your requirement:-
1. I have to add a drop down menu for particular product from which user can search products by size, color, brand etc.
2. I have to make your admin panel easy to editable so that you can upload products by yourself.(I will provide you guidance on how to mange admin panel)
3. I have to add mega menu with custom filter in your site, so that user can easily search products
4. I have to make it Mobile Friendly with basic SEO, so that your website can get high results in google tests.
I have few queries to ask:-
1. Which payment gateways and services do you want to offer? (PayPal, Google Wallet, bank transfer, COD, check/ money etc.)
2. What shippers will you be using? (FedEx, DHL, etc.)
3. How many product categories? Do you need particular search filters for product catalog?
I request you to answer my above queries, so that I can provide you my best offer.
Waiting for your valuable reply.