It's tough to give good advice without knowing more about what you're trying to do.
In general my advice is to invest time exploring cheap channels that are sustainable. Common example: blogging. Easier said than done, but if you create useful content and build a following those are assets that you'll have for years.
The general rule of thumb is to make sure your LTV (lifetime value of the customer) is 3x your CAC (customer acquisition cost). Depending on your business something like AdWords may not be profitable and if you're not careful you can burn through a lot of money.
That said, spending money on ads isn't always a bad thing. You don't really know what your CAC is until you test it, so you may want to set aside a low budget (e.g. $1/day) for experimentation. If your return on that dollar is promising you can start spending more and see if that's maintainable. But without knowing more about your business, it's probably better to spend your time focusing on free traffic sources.
A lot depends on what you're selling. Some businesses can support a larger marketing budget (because the value per customer is high), some can't.
I personally tend to favor inbound channels (blogging, social media, etc.) vs. outbound things like advertising. These take longer, but are more efficient in the long-term.
But, building organic channels takes energy and time -- which always seem to be in limited supply.
Start with 0. See what you can achieve with that. For everything you add in the bucket, measure its throughput maniacally. Do not forget time and money when doing your calculations. Your skills need to be considered too.
Tradeshows, Ads, Paid Articles may start showing results immediately but might not be USP & sustainable for a long term. (Your competition can bid higher, get a bigger booth, etc.)
SEO, blogging, thought leadership, customer support will require time but are more sustainable. (Your site wont disappear overnight etc.)
Traditional marketing, Google Adwords, Facebook, Twitter, Blogs everything is available at your disposal. See what fits your time, money & skill matrix best.
Usually it is a combination of things, over a funtion of time.