I know from my research I need to use canonical, hreflang tags in the code.
I would focus on having each page optimized in such a way to serve your target client within each specific geo location. Simply make sure they don't share duplicate content.
I've recently solved this problem, by launching 5 dedicated domains to scale across our organic acquisition across Europe - and I can offer a lot of actionable value here.
href lang tags will get you so far.. but it depends on the circumstances. For instance, are you an English language site wanting to target USA, AU, CA, IE and the UK? or are you throwing languages (French, Spanish) into the mix as well?
Looking forward to hearing from you, particularly with regard to some more detail.
I can also add value here. First off, you probably don't need hreflang AND canonical, most likely it is one or the other. Second, do the two countries share the same language, or are they different languages? I want to make sure that you actually NEED hreflang, since many sites don't.
Also, I respectfully disagree about building multiple sites (right for some, not for all), especially if you are just starting out. It is best to leverage the SEO efforts that you have already made, and have the second country/language live in a subfolder of your current website.
Let me know if you need more help!