Crypto is a craze. Cannot seem to get subs at all.
Opt-in depends on your offer, how attractive it is to the potential customer, what benefits you offer to your audience etc.
There are a few tips for you:
To buy targeted traffic, you can go to the Find Sellers section.
You can search for vendors by niche name and filter them by sales received from their traffic and reported by their buyers.
Carefully check the ratings given by previous traffic buyers and find the best sellers. Feel free to contact the vendors directly in the Message section if you still have any questions.
Here you'll find a detailed tutorial with a video for buyers: https://udimi.com/help/buyer/how-to-buy
Note that in the Solo Deals section you can find special offers from sellers that can be cheaper than their original price.
There is a lot of useful information in the Help section on the website.