With the limitations your choices are few in so far as powers. One cool thing about the bard is that you can take as many multiclass feats as you qualify for. Your build will look something like this from what you said:
level 1
Gnome, Bard
Bardic Virtue: Virtue of Cunning
FINAL ABILITY SCORES
Str 8, Con 14, Dex 13, Int 16, Wis 10, Cha 18.
STARTING ABILITY SCORES
Str 8, Con 14, Dex 13, Int 14, Wis 10, Cha 16.
AC: 17 Fort: 12 Reflex: 15 Will: 15
HP: 26 Surges: 9 Surge Value: 6
TRAINED SKILLS
Arcana +10, Diplomacy +9, History +8, Bluff +9, Streetwise +9, Stealth +7
UNTRAINED SKILLS
Acrobatics +1, Dungeoneering +1, Endurance +2, Heal +1, Insight +1, Intimidate +5, Nature +1, Perception +1, Religion +4, Thievery +1, Athletics -1
FEATS
Bard: Ritual Caster
Level 1: Twilight Adept
POWERS
Bard at-will 1: Vicious Mockery
Bard at-will 1: Misdirected Mark
Bard encounter 1: Blunder
Bard daily 1: Stirring Shout
ITEMS
Ritual Book, Hide Armor, Light Shield, Wand Implement
RITUALS
Glib Limerick, Brew Potion
It's not necessarily the Bard I'd prefer to play but if sneaky is the way you want to go than sweet as. Personally I prefer the Warlord as leader, but there is nothing sneaky about the Warlord whatsoever, although there is a Charisma build for the Warlord as well.
Anyway, making a character that actually really sucks is quite challenging in 4e, so don't worry too much! Anyway, good luck and hopefully your DM can make the game enjoyable enough that the system becomes less jarring for you.