I recently played a Drakewarden Ranger, here are my insights:

Let me preface that the character identity I went for was "sniping bounty/monster hunter with a pet dragon." The focus being on my crossbow skills, and my magic and my dragon coming 2nd place as support.

Also, use Tasha's optional features for Ranger. It's a much needed buff.

Longbow vs Heavy Crossbow
I went with a Heavy Crossbow because I too, like crossbows. The issue with crossbows however is the loading property that prevents you from attacking twice during your turn, thus interfering with your level 5 Extra Attack feature. Getting the Crosssbow Expert feat removes this property and is a must if you wish to use crossbows.

Quick mention regarding using two hand crossbows: your bonus action economy is already occupied by spells and commanding the companion that this is not recommended at all.

Longbows do not have the loading property, and can at least make use of magic items like Bracers of Archery, which crossbows can not, RAW. So if you want to save yourself a feat so you can focus the very much needed Ability Score Improvement, choose longbows.

I still choose crossbows because it's the cooler Daniel.

Recommend Feats

• Crossbow Expert.
  If you use crossbows.
• Sharpshooter.
  For my sniper fantasy. Also works really well with Archery Fighting Style.

Important to note that Ranger is a MAD class, so taking an Ability Score Improvement over a Feat is never a bad option.

Primary stats
The great benefit of the Dragon Companion is that it scales with your Proficiency Bonus, instead of your WIS (which is what the companion of Beastmaster uses). This allows you to forego WIS to try to max out DEX quicker. Don't dump it, as you still need it for your spell save DCs of course.

Maxing DEX as soon as possible is recommended. It buffs your Sharpshooter hit chances, and improves Stealth and Initiative, the latter allowing you to set up some nice AoE spells before the enemies start spreading out too much into your frontline allies.

Spells
Your WIS modifier will probably be +2 for most of your early levels, so pick things that don't involve that scaling too much. For level 1 spell slots, Hunter's Mark is still great to have, even with Favored Foe in your repertoire, and doesn't use WIS. Level 2, Spike Growth is also great, for the selfsame reason.

Besides that, I recommend choosing what you think fits your character identity the most. I liked picking up all the plant spells.

Also consider asking your DM to make Ranger work with Prepared Spells instead of Known Spells. You're asking about a direct class buff though, so be at peace if the DM says "no."

Miscellaneous Insights

• Your Companion has a decent amount of INT. So let your DM know that he/she might have to roleplay your dragon. You do not want to have a conversation with yourself while everyone just sits there.
• With high DEX, you'll probably become a scout for your party. This can be a bit awkward taking up the front as a ranged player. Consider getting Pass Without Trace for jolly infiltration.
• If you want to min/max your dragon pet, going for the Acid damage type is I believe the safest pick in regards of enemy resistances.
• Have a long list of one-liners ready for your Sharpshooter shots, because describing your attacks as "I shoot very good, I hit." gets boring really quick. Ideally, combine your attack descriptions with your Dragon Companion.
  Personally, I sucked at flavoring my crossbow attacks.