I have 2 commerce feeds imports, one must run before the other
There are multiple solutions to this problem:

Cron manager
One is indeed to use a cron manager module. I think you would need Feeds Ultimate Cron for this. This solution would require you though to guess when the first import is completed.

Rules
Using the Rules action 'Execute feeds importer' (requires latest dev of Feeds 7.x-2.x or the patch from https://www.drupal.org/node/2446307). In this case you would create a Rules component of type 'Action set' and then add two times the action for executing a feeds importer (one for each importer). Perhaps it possible with Rules Scheduler to run this action set on a regular basis? Note that you should configure the importers to not run in background, else both imports may still run simultaneously. Also note that Feeds would try in this case to perform the whole import in one go, so it could perhaps cause max runtime issues.

Drush
Feeds has a drush command called feeds-import with which you can perform an import in one go. So you could create a shell script that runs both imports after eachother and then run that script on a regular basis. For details about this command, see https://drushcommands.com/drush-7x/feeds/feeds-import/

Implement hook_feeds_after_import()
Feeds has a hook called hook_feeds_after_import() that you could use to initiate an other import programmatically:


/**
 * Implements hook_feeds_after_import().
 */
function mymodule_feeds_after_import(FeedsSource $source) {
  // Run product display importer after product importer.
  if ($source-&gt;importer-&gt;id == 'product_importer') {
    $product_display_source = feeds_source('product_display_importer');
    $product_display_source-&gt;existing()-&gt;startImport();

    // Execute batch, if there is any. Set 'progressive' to false to prevent
    // batch from triggering a drupal_goto().
    // (note: this code is not needed when using the 'process in background' option.)
    $batch =&amp; batch_get();
    if (!empty($batch)) {
      $batch['progressive'] = FALSE;
      batch_process();
    }
  }
}