So I've been doing one of these challenges for the past week now and I'm just up to the 8th Gym.
I'm using it in a Nuzlocke kind of way - if it dies, it gets boxed forever and a new Pokemon is received through WonderTrade.
My first 6 Pokemon were:
Scatterbug
Lvl 1 Deino with egg moves!!!
Marill
Eevee
Cranidos
Magneton
Smashed my way through everything with just the Scatterbug, Deino and Marill as the other three were too overlevelled until I got to route 8. Everything was great until Grants Tyrunt OHKOd my Vivillon (Scatterbug evolved) and my Cranidos!
WonderTraded for 2 new Pokemon and then my team was:
Azumarill
Espeon
Deino
Magneton
Durant
Lickitung
Now at this point receiving a level 1 Durant wasn't bad. It has awesome attack stats and I could put up with Truant as it's ability. Lickitung was level 56 so that was not able to be used for ages!
Flew through Korrina, Clemont, Ramos and the Fairy gym easily. Just before reaching Anistar gym I lost my newly evolved Zweilos. DEVASTATED! I can't remember what knocked him out but it really annoyed me. WonderTraded a new Pokemon and received a level 1 torchic with speed boost. Frustrating to get a level 1 so late in game but whatever. I can make it work.
Hit the psychic gym and whilst battling the Medicham I foolishly put out my Durant and BAM it got critical hit KO. Ugh. To make matters worse for in game play I got a level 1 magikarp as it's replacement. Dang.
So now just reached the ice type gym and this is my team:
Gyrados
Blaziken
Azumarill
Espeon
Lickilicky
Magnezone
In all fairness it's a pretty alright team. I'm sure there's a weakness to something that I'm still not picking up on but I feel like it covers most issues.
I also own a Murkrow for Fly purposes.
I really hope I don't lose any more because I don't quite fancy grinding up a level 1 anything again!!