So I got this chunk of wisdom from browsing MWA wiki (yes I also find it pretty funny place to get an advice on other Nutaku games):

Originally Posted by http://millenniumwaraigis.wikia.com/wiki/Thread:45550

For free starters the priority is to get at least 1 5/6 star to level 70. Abuse story maps for the seeds and free gacha the seeds for some bronze/silvers; use this as your main setup for the first 2 weeks while you get your 5 star maxed out. Your helper's strength scales with your highest leveled unit; rely on helpers to help you clear and farm higher tier maps even if you can't 3 star those since the stones aren't your highest priority right now. Depending on your 5/6 star's attribute farm the respective experience fodder to cut your expenses. Sell off the 2 stars and basic gears; you only want to keep +10 intermediates and refrain from equipment upgrade at the moment since it's a huge gold sink.

Note the first and third sentence. I wonder how it actually effects things?