Yes, you can lose an entire weekend just looking at themes

. It's crazy what you can do with WP now.
Never use Weebly if you have any intention of growing your site. Moving to WordPress later will be costly both in time and money.
I would suggest starting by laying out on paper what you must have NOW. And then only evaluate themes that fit that.
That said, you just need to get online NOW. You can stay under construction while you build out and learn WordPress. When you first install WP, it comes with what's called a default theme, called Twenty-Eleven. You can easily change out the 'header image' (large image at the top), column layouts, etc. to have a nice, basic website that gets the job done for now. You can tweak and add as you go and learn more.
Things like sliders, galleries, feeds, and all those bells and whistles can be added into your theme by way of 'plugins' - add-on bits of code that do those neat things.
You can also sign up for an account at wordpress.com and play around with the dashboard (admin panel) there - it's identical to the one you would have when you self-hosted your site on your own hosting account, except you can't install plugins.
I suggest you give THAT a try so you can see before you commit to one or another how you like it.
Hope this helps - it's a pretty vast subject, so start SMALL, bit by bit, to get a good feel for how you might want to use it.
Warmly,
Gower