If its ur baby girl, you can dress her n yourself same colour. It ll look cute n she ll cherish when she grow up watching her Mom n herself dressed up same on her bday.
Wear whatever you want and feel comfortable in. If you want a gharara then go with that, doesn't have to be too fancy, can be a simple gharara. Those ghararas/shararas/dhaka pajamas are in style these days anyways. I wore a sharara/dhaka pajama to my baby's first birthday last year. Then I wore that same outfit to a wedding later on and another birthday too.
I know a lady who wore her valima outfit on her daughters birthday, and one who wore her wedding! All these ladies had kids within the first year of marriage though.
wear a flowy chiffon dress
well I focused more on baby n got a nice embroidered suit for myself,if you are having any themed base party then wear accordingly,i attended a bday party wear baby mum dad all three were wearing same colors. also my friend had tiara themed party where both mum n bday girl wearing tiara, or if you like you can wear sari or simple shirt n trouser, but make sure you are comfortable enough to attend your babyn guest n enjoy bday party as well :)