I guess you wanted to submit to most commonly used databases like NCBI, ENA etc. So, they are public and of course free.
There is no queue to submit the data. (curation can take time depends on the database)
" input is not so complicated" - there is user manual provided by the database for the users to follow. But if the user is not familiar with the terms and computer/bioinformatics terminologies, then this question is very subjective.
most database offers the opportunity to share your data, but it will be for whole omics data. Before applying your single data, take a time and see this paper (Article Gene Variant Databases and Sharing: Creating a Global Genomi...
) il will guide you to choose the one corresponding to the disease you're working on.