Let me instead pose some questions that you need to think about. The answers to these questions will inform your initial marketing strategy and the budget allocation. A few of the questions that come to mind include:
- Are you after SMBs, mid-market or Enterprise segment?
- Related: what's your sales model like - inside sales, direct sales, inbound, outbound?
- Related: how important is "credibility"?
- Are you going after any particular vertical?
- Can you relate your product to something else that already exists in the market?
- Are your potential customers familiar with what you sell? (i.e. does it already have a three-letter-acronym?)
- Is your product complementary to something else
- What is the sales cycle like, who are the relevant decision makers in your account - is there more than one? Are customers going to buy in first or second visit to your site?
- Geographical focus?
You say you have 250 customers already. How did you go about acquiring those customers (assuming they're paid). What's the ARPC, and what's the projected LTV - maybe too early to calculate this, but it is still something worth considering.
Most importantly - I'll question why the goal is to drive traffic. Unless you're selling to a very very broad market (SMBs) with a very very horizontal tool (think domain registration, online backup, etc) - or a wide set of products, traffic is not going to do much for you.
Even if you are, you need to drive the *right* kind of traffic!
I'd argue that at this stage, you want not traffic, but customers to bring cash AND help validate the model for your next funding round (assuming you'll need it). I'm not a VC, but if I were, and I saw your traffic chart spiking up, but your revenue/customer count staying flat - I'd think: "hmmm, people do not seem to want what this company offers!".
Now, that said - from what you mention, I'd just forget about SEO. In my experience, that time is long past gone, and beyond the basics, anything you do there can actually backfire these days. The other tactics might or might not work, depending on your answers to the questions above.
Lastly - sometimes, the best way to do marketing, is to take some of that "marketing budget" and allocate it to something else - build a connector, an integration, freemium model, etc. So when it comes to marketing, you need to keep the goal in mind (customers, revenue) and be willing to forgo some of the more traditional marketing channels (advertising, ppc, etc).
Best of luck!