[title] ...and has very little experience with D&D. The last time he played was 30 years ago. Everyone at the table has little to no experience with 5e, except me, and I don't know the ranger class that well.
I'm looking for some general advice on how to build a decent Ranger with Hunter Archetype by using the PHB only . Advice on Spell choices would be very helpful.
Also, how a DM could handle Favored Enemy and Natural Explorer abilities. Eventually, we'll be exploring The Isle of Dread (Goodman Games version) and i imagine that these abilitie will become super important.
If you are going to play a PHB only ranger then the combination of a hunter and the Isle of Dread is more or less a best case scenario. The other PHB ranger subclass (the Beastmaster) gives you an animal companion that's a liability rather than an asset because it's very squishy and goes down easily. But you've dodged that bullet already. Hunter's bland but decent enough.
Favoured Enemy has a problem in that it's spectacularly situational much of the time - and it mostly just gives you advantage to track (which you don't do that often) against either an obscure enemy type or two subraces of humanoid, plus possibly a language. The key to why it's decent enough on the Isle of Dread is that dinosaurs are beasts. The beast specialty is normally a bad one because you aren't often fighting beasts after level three or so but this doesn't apply here (this applies in general; if you pick goblins as a favoured enemy they may be everywhere at level 1 but by level 5 not so much). The only slight flexing of the rules I'd use is "
you also learn one language of your choice that is spoken by your favored enemies, if they speak one at all" to allow something some D&D animals have learned, for example Sylvan or something some have learned in the circus.
Natural Explorer is, in most campaigns, near useless for two reasons. First most of the abilities only apply "
While traveling for an hour or more in your favored terrain" which is something you don't find a challenge that often most places, with the Isle of Dread being an obvious exception. The second is that for most games the two most dangerous environments are cities and dungeons, neither of which are normally helped by favoured terrain. Meanwhile most of the Isle is either mountains, forest/jungle (they're treated as one terrain type), or coast (which as a generous DM I'd count as any hex with either a speck of sea in it or a hex adjacent to a hex with a speck of sea but I wouldn't count on others being that generous.
Primeval Awareness at level 3 is so situational that it's only better than no level 3 ability at all on a technicality. In Tasha's Cauldron of Everything it's optionally replaced by Primal Awareness which gives you an extra spell known at each spell level and a free cast of that spell.
For build advice archery is the ranged fighting style while duelist is the best melee choice (two weapon fighting is just bad). I'd recommend ranged but both work, using the longbow or the rapier and shield with dex as your primary stat although the rapier and shield combo feels like a second rate fighter. For which hunter ability there aren't normally enough large foes for giant killer to be worth choosing; hordebreaker is amazing on an archer unless you've a jerk DM who always gives you solos or splits their monsters up to avoid your hordebreaker while colossus slayer is reliable. I would add that just about every post-PHB ranger subclass gives you a colossus slayer equivalent plus free spells plus an extra bonus,
Rangers don't get many spells. The standout first level spells are generally considered goodberry (healing + foraging), hunter's mark, ensnaring strike (which competes with hunter's mark for your concentration spell), and longstrider. For second level spells pass without trace is amazing, and spike growth is normally considered a stand-out but not on open ground. That said if there's a druid in the party they get both goodberry and pass without trace earlier than the ranger.
I'd still recommend using rules from Tasha's Cauldron of Everything to fix the ranger but for Isle of Dread in specific and having avoided the actively terrible beastmaster ranger things will be fine.