How to use "at first glance"

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When you first see someone or think about something without having more details, you may say "at first glance" . It's your first impression. Let´s look at some examples?

At first glance the deal looked wonderful, 

but after reading the fine print he wasn’t so sure. 

At first glance, the problem appeared quite simple. 

Later we learned just how complex it really was. 

At first glance, the theory seems to make a lot of sense.

How to use "on second thought"

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"On second thought" is an idiom and it means a reconsideration of a choice, of a decision. It´s "used when you want to change something that you have just said, often to say the opposite"

"On second thought, I don't think I'll go."

It´s important to say that "on second thought(s)" might be also a noun and it means "a revised opinion or idea on a matter already considered". 

"He had second thoughts about his decision."

How to use "go figure!"

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According to the Cambridge Dictionary online, go figure! is used when you tell someone a fact and you then want to say that the fact is surprising, strange or stupid:

It's a terrible movie and it made $200 million. Go figure!