Health is most important, so please take good care of yourself.
Health comes first before anything else, so I hope you'll get well soon.
Health is most important, so please take good care of yourself.
= 健康がいちばん大切なので、どうぞお大事にしてください。
Health comes first before anything else, so I hope you'll get well soon.
= 健康第一なので、すぐによくなるといいですね。
XXX comes first before anything else で「XXが何より大事」、「~第一」という意味になります。
get well soon (すぐに良くなる)の代わりに feel better soon(すぐに気分が良くなる)も使えます。