With that budget, if I had to choose just one traffic source to test a niche, I'd go with tiktok Ads without hesitation, it's not the cheapest, but it gives you the fastest feedback, and with $1,000 you can run real tests, the problem with google Ads is that for new niches, if you don't have keyword data, the cost per click can eat up your budget in two days without you even knowing if the product is working, meta Ads facebook and instagram is fine, but these days the targeting isn't as precise as it used to be, and the cost per impression has gone up a lot, with $1,000 on meta, depending on the niche, you can draw some conclusions, but you risk not getting enough data.
Tiktok Ads has two huge advantages, first, the CPM, cost per thousand impressions, is lower than on meta, so your $1,000 goes a long way, second, the short video format lets you test many creative angles without having to invest a fortune in production, you can record ten different videos with your phone, and tiktok's algorithm will show each one to similar audiences, the one with the best retention and clicks wins, within a week, you'll know if the niche has potential or not, however, the sales funnel needs to be very clear, because tiktok traffic is more about discovery than immediate purchase.