Well, I'm gonna explain the basics of the 2nd Gen remake games. I have a HeartGold but they are basically the same. It'll probably be rather long, since I tend to get ahead of myself, but all the info is straight to the point.
Starter Pokemon:
Chikorita: Probably one of the hardest to start out with due to the first two gym leaders having a type advantage(attacks doing x2 or even x4 damage than normal), and even then it's not very useful against any of the gyms through the game so I wouldn't recommend picking this one since it takes mostly experienced trainers to get through the game with it.
Cyndaquil: A favorite of mine but at the same time not the most useful. It's has an advantage in the second and sixth gyms as well as being able to take down a few of the Elite Four (final bosses that you have to fight in a row without being able to stop and go to the PokeCenter; you can still use healing items though.)
Totodile: Probably the best to start out with. I've used him in both my original Gold and HeartGold and he has a good advantage with few disadvantages early on. It has no advantages or disadvantages through the first two gyms but in the third gym I did have trouble with the leader's Milktank but that can be solved with a little luck and a bit more training. It has an advantage in the forth gym and doesn't have a disadvantage until the sixth where you should have a good enough team to take down the electric Pokemon with no trouble. With Totodile I'd also suggest you keep him as a Croconaw until he reaches level 51 and learns Hydro Pump. Otherwise your Feraligatr will have to be lvl 63 to learn it. You can stop an evolution by pressing 'B' while it's trying to change.
Gyms:
Note: I recommend fighting all the trainers in Gyms. Even if it's not nescissary, it's still good experience for your Pokemon.
First: Flying type based. You really can't get a Pokemon with an advantage so just power up your team to anywhere from Lvl 12-15 (you really only need two at this level).
Second: Bug type based. Fire and Flying work well here. Cyndaquil is the only fire type you can get early on, but it's easy enough to raise a Pidgey or Spearow or even a Butterfree and take them down. A Lvl 16-20 flying type will give you an easy run.
Third: Normal type based. You really can't get a type advantage and you really have to level up good to take down Whitney's Milktank. I believe my starter was lvl 20 (tough run) and my backup Butterfree was lvl 16 or so. It took me plenty of tries to take her down so I'd say level up as much as you can (Lvl 20-25) to face her.
Forth: If you chose Totodile, this Gym is a breeze and you'll really only be going back to the PokeCenter to regain you PP (powerpoints, how your Pokemon attacks). Just use Bite for all the Gastly and it'll be a one-hit-K'O' if he's over level 20. This will also get you a bunch of experience before you face Morty. Just keep Biting!
Fifth: This is where your flying Pokemon will come in handy again. Fighting types are weak against Flying and they can be taken down rather easily.
Sixth: I forgot a lot about this gym, so you're on your own on how to deal with the Magnemite but the Steelix can be taken down with Fire or Water attacks.
Seventh: By now you should have probably found a Mareep (rout 34, 42, 43) so use it's electric attacks on the Seel and Dewgong and on the Piloswine use Water, Gras.s, or Fire.
Eighth: The final and most difficult (I still haven't beaten it but that's because I'm training a specific Pokemon for it). Use Electric on Gyrados and teach your Croconaw/Feraligatr (if you chose that) Ice Beam to take down the Dragonair. As for the Kingdra... you're just going to have to level up and try to overpower it unless you somehow got a Dragon type.
Pokemon To Definitely Grab:
Caterpie: Evolving it into a Butterfree gives you a major advantage at the start, even if you might not use it for the entire run (although I kept it, most ditch it later on). It can use Flying and Psychic attacks as well as Stats inflicting ones. Can be found in Ilex Forest or even before that.
Recommended Moveset: Confusion, Gust (or another flying move you can teach it), Sleep Powder (works wonders when you're facing a stronger opponent that you need a few extra shots at), Poison Powder (chips away the health for you but they can still attack you.
Mareep: The best electric type to get close to the start. Period. Evolve it into Flaaffy then immediately into Ampharos in order to learn ThunderPunch. Other than that, the moves are up to you until later when you should teach it Power Gem and Signal Beam.
That's all I can write at the moment. Told ya I'd get ahead of myself, but I really think this will help for a beginner. That's good enough to start out with and if you need any more help or anything else explained, just ask. I'll keep an eye on this thread ;3