Id say as a finisher a thuri can be nice and basic. Like an Arkie they are basic stones. But all Natural stones take time to learn. Syntetic stones are the best when learning to hone as they are straight forward. Less of a learning curve.
Having synthetic stones to work your way up then finishing on a Natural is the way to vo if you want to do Naturals. Or open your wallet and buy a few Jnats and cross your fingers. As that swimming pool is expensive to play in and you may not ever get a great edge.