I've never had a voice acting career, but I plan to have one soon. These are my tips you should follow to get the voice acting career of your dreams:
Gradually get into bigger projects - First, you should start in small projects then gradually get into bigger projects. That way, it should be easier to take on larger voice acting projects, such as voicing characters with lots of spoken dialogue.
Make your own voice acting demo reels first - Make sure the recordings are in high quality and that they're done in a quiet, silent or soundproofed area. There's two types of voice acting demo reels you could do (you can do any of them or even multiple of them): impressions (made of you trying to make your voice sound like various real people and fictional characters) and types of voice (made of trying to make your voice sound different from your normal voice, but not as impressions of other real people and fictional characters).
Watch anime and animation with awesome voice acting - The voices they have could inspire and help you to make more awesome voices. For example, watching this anime clip over and over again could help you to perfect an anime girl voice to some degree.
Watch "Undertale Voice Acting" videos - The voices put on in such videos could inspire and help you to make more awesome voices. There's some examples here. You'll most likely find some Undertale voice acting videos from Timber Puppers and The Nth Human, along with some Undertale voice acting videos uploaded by others.