Most replies here focus on individual programs (Amazon, ClickBank, CJ), but worth separating two things: programs (one product/brand) vs networks (aggregate hundreds of offers under one dashboard). For a true beginner, networks tend to be more efficient since you're not juggling 10 separate logins and payment thresholds.
The 'easy approval' ones mentioned above (ClickBank, Rewardful-based SaaS programs) are solid for digital products. If you want broader reach across verticals, look for CPA/CPM networks that explicitly advertise beginner-friendly approval — payout terms and minimum thresholds vary a lot though, so it's worth comparing a few before committing serious time