Before you spend anything you first need to determine how much you want to spend to acquire 1 customer. An acquisition could be a purchase, membership signup, email submission, etc. Let's say you can spend $30 per customer. (You might find that your cost of acquisition is very low and that this kind of advertising just doesn't make financial sense before you even start)
Now because you are just starting your testing you should assume that hitting your target will be 2-3 rounds of testing down the road. Because of this test only enough money in each channel or platform so you can get a signal as to whether you are at least in the ballpark of your cost of acquisition.
- For $30 cost of acquisition I'd spend $100-150 per individual test. (a test may be a platform, an individual ad, a targeting method, a landing page, copy etc.). If you don't get 1 conversion then you either iterate and try alternative ads, copy, etc. Make sure when testing to only change one thing at a time so you can learn.
- Even just 1 conversion is valuable information. It shows that conversions are possible.
- No conversions - you will need to do more testing
Spend your $1000 increments and make sure you are paying to get learning because otherwise it is just gambling.
- Stay away from retargeting until you have at least 10k monthly website uniques.
- I would start with Facebook Ads and Google Adwords - although adwords is extremely competitive and will most likely cost more if your industry has competition. I've made businesses work on those 2 platforms alone.
- Linkedin and bing don't have a lot of volume so you might be wasting you time - although not impossible they will be harder to make work than FB or ADW.
Hope this helps you out! Best of luck and let me know if I can be of help further.