Chose Snivy for a starter (so I could get Panpour for free, for a water HM slave later). Spent a long time turning circles in the grass on Route 1 before I came up with the Lillipup I wanted - Adamant with Vital Spirit (which becomes Intimidate with Herdier and Stoutland). It's a male and I caught him at level 2 and named him Sebastian.
Then we went on to Accumula Town, without encountering anything along the way.
Walked out of the PC, planning on going back down to Route 1 to train Sebastian a bit, but when I saw the crowd over by the square, I decided to get that part of it out of the way first. That turned out to be a tactical error, but I didn't realize it until the crowd broke up and I saw N, and remembered that that's the first time you have to fight him and here I was, preparing to do a solo run, with a level 2 Lillipup. Nothing to do about it though, and I had just bought seven potions, so I figured I'd give it a shot.
That was one of the more thrilling battles I've had in a while. N's Purrloin is level 7, and each of its Scratches did 5 points of damage to Sebastian, who only had 14 points total. So the first hit knocked him down from 14 to 9, then he hit back with a Tackle and took off maybe 1/8 of the Purrloin's total. The next hit knocked him from 9 to 4 and he hit back with another Tackle. On the next turn, I gave him one of the Potions to bump him up to 14, then the Purrloin hit to knock him down to 9. Next turn, the Purrloin hit to knock him down to 4, then he hit back and took a little off. And that became the pattern - every other turn I gave him a potion, then he got in a hit, then I gave him a potion, then he got in a hit. All I could do was hope the Purrloin didn't get a crit while he was at 9. It only got one though, and it came while he was at full health, knocking him from 14 all the way down to 3. And in the end we won. It took all 7 of the freshly purchased potions (I only had one left - the one from Route 1) and after the battle, Sebastian went all the way from level 2 to level 6. Unfortunately, I got so caught up in the battle that I forgot to grab any screenshots. I took the money from the battle, plus what I had left over, and bought some more potions.
From there on out, it's been surprisingly easy. We breezed through Route 2, including battling Bianca at the end of it (Yes Bianca, you are in trouble). Got in to Striaton City and fought Cheren at the school, then went to the Dreamyard and picked up the Panpour and named him Carl. Cruised through the first gym.
Then we went back to the Dreamyard. Taught Carl Cut and went in and fought the grunts, and Sebastian reached level 16 and evolved into Herdier.
I wondered what was going to happen with the double battles - the first one is the twins in front of the Day Care on Route 3. Turns out they won't battle you, and won't let you past, unless you have two Pokemon. I had put Carl in the PC after the Dreamyard, so I went back and got him out, but then I had to figure out what to do with him. The only non-attacking move he had was Leer, which still has an effect on the other team, so he still would've been helping out in any fight and it wouldn't be a solo run. So I taught him Work Up via TM, then went and fought the twins. Sebastian did all the work while Carl just stood there and Worked Up (and he only had to do it twice, since Sebastian one-shotted their Purrloins on consecutive turns), so I figure it still counts as a solo run. Best I can do anyway, since they insist on a double battle.
Then on to Nacrene City. Fought N outside the Museum, swung out and around outside Pinwheel Forest (though no Fighter in my party, so no Star Piece from the Challenge Rock), then back to Lenora's gym. Sebastian was level 21 going in and level 23 by the time we worked through the underlings. Lenora (and her Watchog) were the first real challenge since N's Purrloin all the way back at level 2, but it was never any real danger. Its Retaliates took a bit over a third of Sebastian's points, and I had plenty of potions and plenty of patience, so it was just a matter of time.
Finished, got the badge, then it was on to Pinwheel Forest to fight the trainers and recover the skull, then across Skyarrow bridge (easily one of my favorite things ever in any Pokemon game) and on to Castelia City.
Explored the whole city, fought all the trainers, met Burgh, fought the grunts, got that warm feeling when Bianca was reunited with her Munna, and saved just inside the door to Burgh's gym.
This whole thing has been much easier than I even expected. I sort of expected to end up overleveled, even though we haven't ground at all (and haven't even seen a lot of Pokemon, since we only go through the grass as much as necessary to get from point A to point B), just because Sebastian fights every trainer battle and gets every experience point. But we're about 10 levels beyond anything we see in random encounters and at least three or four levels beyond even the toughest trainers. Sebastian one-shots almost everything, and most often with Tackle. He uses Rock Smash on Rocks and Darks and sometimes Normals and Crunch on Psychics and such, and that's it. He had Take Down for a while, but never used it much since Tackle does plenty, and without the recoil.
Currently at Burgh's gym, Castelia City:
Sebastian the Herdier, male, level 29
Adamant / Intimidate
-Tackle
-Crunch
-Rock Smash
-Work Up