Where should I do paid advertising? Facebook or Google?
How Google Ads Work
Google Ads are served to people who are actively searching for businesses like yours in Google Search.
You pay per click and the cost of those clicks is determined by demand & competition for the keywords you use.
Google Ads are great for creating an opportunity to sell to a person who already has an intent to buy what you sell.
How Facebook Ads Work
Facebook Ads are like "smart billboards" meaning they just show up to people who aren't necessarily looking for a business like yours, but are likely to be interested based on their personal information. The more you spend, the more people see your advertisement.
Ideally, you use these two platforms in conjunction with each other. However, if you have a limited budget, your decision should be based on whether or not you need to create more demand for your product, or not.
Facebook Ads are great for building brand awareness and an engaged audience, therefor creating demand.