Agree with Falling into Your Smile. For a beginner who used to watch K-dramas where there's what people called visual worship and pale skin worship, Xu Kai's drama is a good choice. And maybe (I'm biased) Yang Yang in Love O2O. Actually Lin Yi is also a good choice, he's pretty much a complete package (tall, handsome, and pale; but I'm not sure if his nose suits KBS 😅). It's just I only completed one of his drama; Memory of Encaustic Tale. It has some similarity with (imo) Reply 1994. And oh yeah there's Wei Zhe Ming too in Perfect and Casual. The plot is average but somehow has charm.
If previously this beginner only watch Japanese drama with usually cheerful or strong-willed FL where even rom-com has life advice with shorter episodes; maybe When I Fly Towards You will be a good choice. And maybe Love in Time and Unrequited Love (has this calm and slow vibes like some J-movies).
For costume drama, I always think The Untamed, Eternal Love and Love and Redemption are beginner friendly. But I haven't completed any costume drama (non-short) in the last 7 months (the last one was The Patriot Yue Fei and it's old and not beginner friendly), so I don't know if there's newer suitable choice.
For beginner who used to love adventure or martial art anime, The Immortal Ascension, I Am Nobody and The Spirealm may be suitable.
For thriller lover, sadly I haven't watched many titles except for detective dramas like what I think as beginner friendly dramas; Under the Skin, Guardian and Love Me If You Dare.
From Thai lakorn watchers moving to C-drama, I think they would love soap opera style, with never-ending conflicts and problems like Go Ahead and Best Choice Ever. Would love to recommend costume drama like Story of Ming Lan but it has 70+ episodes x 45 minutes. And Love Like the Galaxy has 56 episodes.
Republican drama is never beginner friendly, with some people hating them, saying things about propaganda. But I can't help but recommend one title only; Winter Begonia.
Recommendation could be a hit or a miss. Watching their trailer to get an insight is one way to check whether it suits one's taste or not.