I have a three year old girl child . I wanted a good investment plan which will look after my child education and marriage expenses.

You might try one of the education savings accounts. It's similar to a Roth IRA in that it's taxable now, but earnings and then distributions later are tax free, as long as it's used for (qualified) education. And of course there's a penality if you use it for something else.

You can go any of the brokerages like Fidelity, Vanguard, T Rowe Price, etc and check and see what they have. As with IRA's these can have automatic monthly investments, and the minimums can be lower than other investment accounts. Just for example:
College Savings Plans: FAQs - T. Rowe Price????? (http://individual.troweprice.com/public/Retail/Products-&-Services/College-Savings-Plans/T.-Rowe-Price-College-Savings-Plan/FAQs)

That isn't appropriate for the wedding plans of course. But that's a long-term goal. Those sites usually also have tools where you can enter your goal and assess your risk tolerance and then give you an idea the type of things you may want to invest in. You don't have to invest in their specific stuff, since of course they're trying to sell you something, but you can follow the types of things they suggest.