PropellerAds accepts small sites with no meaningful traffic minimum and supports reward-based ad models, pop-unders, push notifications, and native ads. It's the go-to recommendation for publishers who can't get into mainstream networks.
For that traffic level with ad-locked content your best bet is probably Adsterra or PropellerAds because they accept lower volume sites and allow reward-based models, but RPMs will still be pretty low at maybe $1-3 until you hit 10k+ monthly visits.
PropellerAds - They accept smaller traffic volumes and are known for display ads, pop-unders, and native ads.
The default starting point for most publishers, AdSense offers unmatched fill rates and brand-safe advertisers. RPMs are modest at low traffic volumes, but reliability and ease of approval make it the consensus first choice.
Mediavine is the premium network publishers aspire to, with RPMs that dwarf AdSense once you hit traffic thresholds. Journey by Mediavine now accepts sites from 1k sessions, making it accessible to smaller blogs while offering a clear upgrade path.
Monumetric accepts publishers at 10k+ pageviews and pays meaningfully better than AdSense, with a low $10 minimum payout that ensures monthly payments even at modest traffic. Community consensus rates it above Ezoic for small publishers.
Media.net is Yahoo/Bing's contextual ad network and performs especially well for English-language content targeting tier 1 audiences. It's a strong AdSense complement or alternative for publishers with US/UK/CA traffic.