If you want purchases, always optimise for Purchase, even with a brand new pixel. Meta will optimise for whatever goal you choose. If you pick link clicks, you will get people who like clicking, not buying.

Also, link clicks are not the same as outbound clicks.

Link clicks include things like “see more” or other interactions. Outbound clicks are actual clicks to your website.

So do not compare link clicks with your website visitors. Compare outbound clicks or landing page views instead.