I’d recommend waiting to buy both ARR and HW, although really you should try it out first before spending much more money than you want, cause you might not like the game. The reason you should buy HW though, is that you can only play up to level 50, that’s like paying for half the game when you only buy ARR. For one thing, the story for you would end after your level 50 quests, you’ll need HW to get to any of the recent content which is a lot more easier to play as most players will be doing active content, rather than dead content.
Since they released the Palace of the dead, leveling wont be so bad now. Sure one could say skip all the cutcenes and story dialogue for faster progression. But why sub a mmo if you are going to skip content to rush progression? It wouldn’t be worth the buy period if you are going to do all that. My biggest advice to new players would be to enjoy the story as much as you can while getting used to crafting and don’t worry about endgame content b/c it could either make you impatient or demoralize you with alot of catching up to.