Setting up a store is actually not that difficult, however, making sure that youhave high conversions becomes a little tricky.
You can begin with just a simple and free Shopify theme if you do not want to spend any money, that is completely fine.
However, if you will want to later get a little more advanced because it can increase your conversions you might want to get a professional theme.
Shopify themes usually can be anywhere from $30 to $100 depending on how good it is.
Most important to increase your sales you will want to start using Shopifyapps.
It depends a lot on what kind of apps you use, you can just use some free ones, but you can also spend hundreds of dollars per month.
You should checkout the Booster Theme I recommend because it has all the necessary plugins already integrated into it, so you can save up a ton of money.
For this part, for the beginning, you can do it for free if you really want to save up money.
Besides the theme, you also need some branding, like your logo. If you know how to use Photoshop that is great.
However, if you do not know how to do it, do not worry you can use websites like Fiverr to get a design for as low as $5.
Related: ‘Why 95% Of Shopify Stores Fail‘