Like most things in web development there are 100 ways to slice that pie - so this answer is by no means all encompassing of all ways to do so.

Depending on what your objectives are I would recommend one of two ways:
1. Use the built in WP gallery feature tied to the WP core. No extra code and thus you couldnt get any lighter than that. It already resizes the images to different sizes. To access simply goto "insert media" and look in the upper left hand sidebar for the gallery option, select your images, determine size, press insert. If you want to customize the wp core gallery functionality to show attributions or something similar a good wp coder could knock it out in 30 min or less.
2. If you want a lot of features and customizations an display and interaction I would recommend just getting Revolution Slider. It has more features than you could ever need and it can pull images into galleries OR it can pull posts in from WP and use the featured image, title, and any other custom field you have into the slider.

There is a lot more that could be said but that is a quick - to the point - response.

Cheers!