having product addons that cost extra $$?

If your product has one option such as Gluten Free Yes/No this is called a Simple Variant. When the customer chooses a more expensive variant, the price will be updated. You can learn more here: Adding basic product variants. 

If your product has many independent options, these are known as Complex Variants. With complex variants, the price won't be updated until the customer has selected an option in all the dropdowns. You can modify this behaviour, so that the price is always updated live, by using our Variant Pricing extension. 

I hope this helps. If you need more assistance, it will really help us if you include a working link to the product on your site. If your site isn't live yet, we will only be able to view it if you set a site password and tell us what it is.