If you can only attend one a year, then do so. Not only do the workshops inspire you to write, write, write, but the contacts made and information passed through casual conversation at these gatherings are invaluable. Study the conferences available to see which offers what will do you the most good. Now that the national RWA conference has only group appointments for editors and agents, you might want to target a conference with individual appointments. Some conferences are casual while others are more formal.
Some conferences offer multi-genre workshops and authors.
Others have a more specific focus. Ask others which conferences they recommend and why. Participate in a critique group . Almost every published author I know belongs to a critique group and meets regularly. That isn't to say you must have a published member in your group.