Best Fertilizer for Indoor Bonsai: Recommendations Needed!

Hi everyone,
I’m relatively new to bonsai and currently have a small indoor Ficus bonsai that I’m trying to nurture. I’ve been reading about various fertilizers, but I’m a bit overwhelmed by the options.
Could anyone recommend a specific type of fertilizer that works well for indoor bonsai, particularly for a Ficus? I’m looking for something easy to use and effective. Also, how often should I fertilize, and are there any particular signs I should look for to know if my bonsai is thriving?
Thanks in advance for your help!