Ascendant Shards are a pain to get.
There's certain things that give you a chance at getting Ascendant materials, which would be Ascendant Shards or Ascendant Energy:
Doing your first Gold tier public event for the day gets you a reward at the post master, which has a chance of being Ascendant materials.
Completing any further gold tier public events grants you a chance of receiving ascendant materials as an instant reward, but these aren't common.
Breaking down Legendaries is a good way of getting them....weapons give energy, armour gives shards (other than your class item)....I would also suggest wearing said armour and levelling it up, right up to the point where you need to use ascendant shards as I think it gives you more shards, I've certainly had 3 shards for a piece of armour a couple of times.
Buying and breaking down Exotic armour is also a good method as you're limited on what you can buy with all of those Strange coins and you can only wear one exotic piece of armour at a time...so buy up additional exotic armour, level it up and break it down for shards!
Another guaranteed method of gaining Ascendant materials is to do the daily missions and weekly strikes, but you only get the rewards for the first time you do it and you need to increase the difficulty....still, a good solid method of getting the materials and the higher the difficulty you can manage the more ascendant rewards you get.
You may also get Ascendant materials dropped when killing bosses or completing missions I think, but the other methods are far better.
And remember, this stuff is required for the highest level armour so don't expect it to be easy to get, it's not.
), now to level up that badboy
Just need to level up the hunter next