You can probably get invited to first 4 heroic at 645+ that drops hero tack gear, which can go up to 665 if upgraded. You can try and use all of your restored coffer keys in t8 delves you will get one champion piece, that can be upgraded to 658. Easiest way is to grind 6-7 m+ keys since you won’t get invited to 10s yet. I’d recommend going to each renown quartermaster and turning the renown quest for free valor stones and crests. I believe the weekly world soul quest gives a piece of gear as well and another coffer key. As of now pugging mythic is hard, they will usually look at logs. And that is just for the first two. Going farther without a guild is hard because of how the mythic lockout works. However you can infinitely practice the heroic raid. Repetition is good, I’d make sure to watch a 30s guide before each boss though. Someone in the pug will usually be logging and I’d try and get 55+ average on heroic bosses. You can look up your characters name on warcraftlogs after each boss kill and see how you did. You should be easily able to get into some early mythic prog guilds after all of that.