Exotic shards are easily farmed in Destiny 1, with only a small cost of motes of Light and Glimmer
1) Consume a heavy telemetry (can bought from the Gunsmith)
2) Go to the Exotic Weapon kiosk, and purchase a heavy weapon for the cost of one exotic shard and 2,500 glimmer
3) Equip the heavy weapon, as well as any other weapons and armor you want to level up
4) Consume 6-ish Motes of light. That will completely unlock all the perk circles of the weapon. DONT put any resources into the perk circles AKA dont click them
5) Dismantle the weapon
This will give back:
- TWO exotic shards
- Between 250 and 300 glimmer
- Between 5 and 10 weapon parts
Use the two exotic shards to buy two more heavy weapons, and repeat the process. Keep an eye on all your other weapon and armor slots and keep items equipped that you want to level up.