I don't understand why the Republic was so interested in the planet Naboo; it's a small planet in a big Galaxy. Queen Amidala didn't agree with the taxation of trade routes to outlying star systems, it's clear, but the Republic wants to have access to these planets uncontended. Why is Naboo so important to the development of the Republic?
Actually, you have it flipped around. It was the Trade Federation that was protesting the taxation of trade routes by the Republic. Thus they blockaded Naboo, which would in turn cause that planets senator to plead to the senate to repeal the taxation. Naboo was selected because Darth Sidious wanted Palpatine to protest and call out the corruption in the senate.
I'll quickly summarize the what's going on on Naboo:
A Muun sith lord named Darth Plagueis is the puppet master behind the events leading up to episode 1, along with his human apprentice, Darth Sidious AKA Palpatine. He operates under the name Hugo Damask and as CEO of Damask Holdings, a financial firm. He learns about a large store of plasma, which is an extremely valuable energy source, beneath the crust of Naboo. So in secret he sets up a deal with the Intergalactic Banking clan, Damask Holdings and a political rival of the current king of Naboo. In return for giving Damask Holdings and the IBC rights to the plasma, they will sabotage the political situation so that a fella name Bon Tapalo will become king.
So now Darth Sidious has been manipulating the Naboo situation by telling the Trade Federation to sell the Plasma at a huge markup, selling the Naboo short. This causes unrest and eventually sparks a military conflict and Blockade. Also, at the same time, the King of Naboo is assassinated (set up by Plagueis) so that Padmé Amidala will be elected Queen. Then Episode 1 starts!
TLDR; The Trade Federation had a monopoly on a resource the planet had invested all its money in, so they jacked up the markup and paid Naboo very little, causing unrest, poverty and eventually the Battle of Naboo.