Best agent for beginners

There is no best Agent and no best Agent to start.

If you get into the game you need to learn a lot. You learn, the maps, the gunplay and the agent you are playing. Until you learn the meta you should have played all of the free ones and have unlocked several others (or even all).
Every agent is part of a special role. For example: entry fragger/duelists, utililty/smokes, lurker. You have defensive specialists and offensive specialists. There is a best agent for your playstyle, but without knowing how you play, no one will know.

The answers of the ppl are maybe just their favourite character (as the most think they need to play duelist because they are the best f... players). Valorant is a TEAM game. You ca win a round alone, but not the game. Find your playstyle and search the agent which is fitting for your style (and adapt, what the team needs).