This custom hook allows you to reward users viewing content based on the category the post belongs to. Goes into your child theme's functions.php file or custom plugin.

mycred-view-content-category-hook

/**
 * Register Custom Hook
 * @since 1.0
 * @version 1.0
 */
add_filter( 'mycred_setup_hooks', 'mycred_pro_register_view_content_category_hook' );
function mycred_pro_register_view_content_category_hook( $installed ) {

	$installed['view_category_content'] = array(
		'title'       => __( '%plural% for Viewing Content (Categories)', 'mycred' ),
		'description' => __( 'Award users points for viewing content based on category.', 'mycred' ),
		'callback'    => array( 'myCRED_View_Content_Category' )
	);

	return $installed;

}

/**
 * Add References
 * @since 1.0
 * @version 1.0
 */
add_filter( 'mycred_all_references', 'mycred_pro_add_custom_references' );
function mycred_pro_add_custom_references( $references ) {

	$categories = get_categories( array( 'hide_empty' => false ) );
	if ( ! empty( $categories ) ) {
		foreach ( $categories as $cat ) {

			$ref = 'view_post_' . $cat->slug;
			$ref = sanitize_key( $ref );
			if ( ! array_key_exists( $ref, $references ) )
				$references[ $ref ] = sprintf( __( 'Viewing content in %s', 'mycred' ), $cat->name );

		}
	}

	return $references;

}

/**
 * Load Custom Hook
 * @version 1.0.1
 */
add_action( 'mycred_load_hooks', 'mycred_pro_load_view_content_category_hook' );
function mycred_pro_load_view_content_category_hook() {

	class myCRED_View_Content_Category extends myCRED_Hook {

		public $categories = array();

		/**
		 * Construct
		 */
		function __construct( $hook_prefs, $type = MYCRED_DEFAULT_TYPE_KEY ) {

			$this->categories = get_categories( array( 'hide_empty' => false ) );

			$defaults         = array();
			foreach ( $this->categories as $cat )
				$defaults[ $cat->slug ] = array(
					'creds'     => 0,
					'log'       => '%plural% for publishing content',
					'limit'     => '0/x'
				);

			if ( isset( $hook_prefs['view_category_content'] ) )
				$defaults = $hook_prefs['view_category_content'];

			parent::__construct( array(
				'id'       => 'view_category_content',
				'defaults' => $defaults
			), $hook_prefs, $type );

		}

		/**
		 * Run
		 * @version 1.0
		 */
		public function run() {

			add_action( 'template_redirect',     array( $this, 'content_loading' ), 999 );

		}

		/**
		 * Content Loaded
		 * @version 1.0
		 */
		public function content_loading() {

			// Only applicable on single post type view by logged in users
			if ( ! is_singular() || ! is_user_logged_in() ) return;

			global $post;

			$user_id             = get_current_user_id();
			$data                = array( 'ref_type' => 'post' );

			// Authors can not get points for viewing their own content
			// Excluded users can not get points
			if ( $post->post_author == $user_id || $this->core->exclude_user( $user_id ) ) return;

			// Get all the categories this post is assigned to
			$assigned_categories = get_the_category( $post->ID );

			if ( ! empty( $assigned_categories ) ) {
				foreach ( $assigned_categories as $category ) {

					$reference = 'view_post_' . $category->slug;
					$reference = sanitize_key( $reference );

					// Make sure we are not over a limit (if set)
					if ( $this->over_hook_limit( $category->slug, $reference, $user_id ) ) continue;

					// Make sure we only get points once
					if ( ! $this->core->has_entry( $reference, $post->ID, $user_id, $data, $this->mycred_type ) ) {

						$this->core->add_creds(
							$reference,
							$user_id,
							$this->prefs[ $category->slug ]['creds'],
							$this->prefs[ $category->slug ]['log'],
							$post->ID,
							$data,
							$this->mycred_type
						);

					}

				}
			}

		}

		/**
		 * Preferences
		 * @version 1.0
		 */
		public function preferences() {

			foreach ( $this->categories as $cat ) {

				$prefs = shortcode_atts( array(
					'creds'     => 0,
					'log'       => '%plural% for viewing content',
					'limit'     => '0/x'
				), ( ( array_key_exists( $cat->slug, $this->prefs ) ) ? $this->prefs[ $cat->slug ] : array() ) );

?>
<div class="hook-instance">
	<h3><?php printf( __( 'Posts in: %s', 'mycred' ), $cat->name ); ?></h3>
	<div class="row">
		<div class="col-lg-2 col-md-6 col-sm-12 col-xs-12">
			<div class="form-group">
				<label for="<?php echo $this->field_id( array( $cat->slug => 'creds' ) ); ?>"><?php _e( 'Amount', 'mycred' ); ?></label>
				<input type="text" name="<?php echo $this->field_name( array( $cat->slug => 'creds' ) ); ?>" id="<?php echo $this->field_id( array( $cat->slug => 'creds' ) ); ?>" value="<?php echo $this->core->number( $prefs['creds'] ); ?>" class="form-control" />
			</div>
		</div>
		<div class="col-lg-4 col-md-6 col-sm-12 col-xs-12">
			<div class="form-group">
				<label for="<?php echo $this->field_id( array( $cat->slug, 'limit' ) ); ?>"><?php _e( 'Limit', 'mycred' ); ?></label>
				<?php echo $this->hook_limit_setting( $this->field_name( array( $cat->slug, 'limit' ) ), $this->field_id( array( $cat->slug, 'limit' ) ), $prefs['limit'] ); ?>
			</div>
		</div>
		<div class="col-lg-6 col-md-12 col-sm-12 col-xs-12">
			<div class="form-group">
				<label for="<?php echo $this->field_id( array( $cat->slug => 'log' ) ); ?>"><?php _e( 'Log Template', 'mycred' ); ?></label>
				<input type="text" name="<?php echo $this->field_name( array( $cat->slug => 'log' ) ); ?>" id="<?php echo $this->field_id( array( $cat->slug => 'log' ) ); ?>" placeholder="<?php _e( 'required', 'mycred' ); ?>" value="<?php echo esc_attr( $prefs['log'] ); ?>" class="form-control" />
				<span class="description"><?php echo $this->available_template_tags( array( 'general', 'post' ) ); ?></span>
			</div>
		</div>
	</div>
</div>
<?php

			}

		}

		/**
		 * Sanitise Preferences
		 * @version 1.1
		 */
		public function sanitise_preferences( $data ) {

			foreach ( $this->categories as $category ) {

				if ( isset( $data[ $category->slug ]['limit'] ) && isset( $data[ $category->slug ]['limit_by'] ) ) {
					$limit = sanitize_text_field( $data[ $category->slug ]['limit'] );
					if ( $limit == '' ) $limit = 0;
					$data[ $category->slug ]['limit'] = $limit . '/' . $data[ $category->slug ]['limit_by'];
					unset( $data[ $category->slug ]['limit_by'] );
				}

			}

			return $data;

		}

	}

}