I'm by no means an SEO expert but generally speaking most SEO related improvements are gradual. It can often take 6 months before you fully benefit from some changes. There are a few exceptions to the rule but most of these would only be relevant if there are issues preventing your site from ranking as it should. i.e. poor URL structure, incorrect use of canonical tags, duplicate content etc.
Paid traffic on the other hand should be far more tangible and should yield you instant and measurable results. You should be aware of your ROI and at what point you're happy to acquire customers. With this knowledge you'll be able to determine the worth of any traffic you're driving through these channels.
Part of any SEO strategy also needs to understand where your pain points are for customers. Minimizing these will often be far more valuable than driving extra traffic to your site as typically 95% of visitors do not end up converting into a sale.
I hope that's helpful.