E-com meta ads vs App install campaigns? we got $1000 to market our new ios app and need help

hey marketers,

me and my freind are trying to scale our mobile app. im the developer and he is doing the marketing (he run ecommerce business with meta ads).

we tested the app in android and got 3 annual subs with only seo. now we launching ios version and have strictly 1000 usd budget to start. we planning to do video campaigns.

since he already know meta ads for ecom, we thinking to use meta for app installs. but we know selling physical product is very different from app installs and subscriptions. this 1k is our only money (i am broke and he is funding) so we need to be very smart.

some questions for app marketers:

is meta still good for app subscription with small budget or look somewhere else?

what we should track or setup before spending money so we dont bleed money?

what is the big mistakes when ecom marketer doing app marketing?

looking for your dos and don'ts so we make this 1k count. thank you