Assassin Archer Gear

As an Assassin, you should attack from stealth as much as possible and you want the maximum amount of damage for a single attack. Those are your crafting and gear goals.

The maximum damage is a combination of buffs, starting with critical chance/critical damage, attack, and flanking bonus, in pretty much that order.

So that means you want gear that maximizes those attributes. For crafting, that means lots of leather offense and utility slots, and metal offense slots. Leather Utility slots are particularly useful, because you can put Bear/Great Bear skins in that slot to boost Dexterity, which gives you buffs to both critical chance damage and attack.

For bow schematics, I prefer tier 3 or 4 bows that are upgradable, because grips can add a lot of leather and metal slots. Some recommended schematics: Swan Longbow, Knight Commander Longbow, Masterwork Spiked Longbow, Elgar'nan Enaste, Grunsmann's Bow, Bow of Beresaad. The bolded one is my favorite. For grips, pick one with a lot of leather offense or utility slots, like the Thick Longbow Grip or the Wrapped Longbow Grip.

For armor schematics, the choices are much simpler. Pick one of these two: Superior Prowler Armor or The Skin That Strikes. The latter breaks my rule of upgradable gear only, but since it is part of the The Taken Shape which has a lot of good buffs, it stays on the recommended list. For upgrades, again, pick as much leather or metal as you can, or pick defense buffs that you might need, like cold resistance. Prowler Armor arms and Hunter Coat legs are good choices, but you can decide for yourself.

I would not recommend starting out in Haven with those schematics, you'll be too overpowered. Wait until you have your Assassin specialization in Skyhold and at least 12 skill points to spend. Then you can get the most out of that gear. Use the general guidance above to decide on Tier 2 and lower gear to use.

For materials -- use the guidance above. You will obviously want high tier leather and metals, for example: bear/great bear skins, lurker scales, craggy skin, snoufleur skin, everite and silverite.

For Fade-Touched Masterworks: Hidden Blades 3x and 4x and 5x (pick any two that don't match, like 4x and 5x), move faster while in stealth, Walking Bomb, +max stamina.

For other gear, like rings, amulets and belts ...

Rings: Enhanced Hidden Blades, Critical Chance, Critical Damage, Attack, Ring of Slicing, Superb Ring of Attack, The Hand That Cuts.

Amulets: any cooldown, any dexterity or cunning, Amulet of Death Siphon, any renewal, Malika's Guard, The Eye That Weeps.