You might be better of seeking advise from those that created WooCommerce, in general we can't support third party scripts (personally I have no experience with WooCommerce).
In general, cache plugins can be useful, if configured right. Making sure images are small and properly compressed helps as well, limiting how many plugins you use can have an impact.
Sadly, WooCommerce, and other webshops, tend to be a bit resource hungry and may not always be a good fit for free hosting in the long run, especially not if you have a lot of products in the shop.