There is nothing wrong with accepting a gift and giving something of similar value to the giver
Question

One of my relatives sent me a large amount of money on the occasion of my marriage, with the intention of helping me. Should I accept it or is it better to refrain and be content with what I have?.
Praise be to Allah.Al-Bukhaari (2585) narrated that ‘Aa’ishah said: The Messenger of Allah (peace and blessings of Allah be upon him) used to accept gifts and reward people for giving them. 
“Reward people for giving them” means giving the giver something of equal value at least in return. This was the view of al-Haafiz in al-Fath. 
This hadeeth indicates that accepting gifts and giving something of equal value to the giver is the way of the Prophet (peace and blessings of Allah be upon him). 
The Prophet (peace and blessings of Allah be upon him) enjoined responding in kind to favours, as he said: “Whoever does you a favour, respond in kind, and if you cannot find the means of doing so, then keep praying for him until you think that you have responded in kind.” Narrated by Abu Dawood, 1672. classed as saheeh by al-Albani in Saheeh Abi Dawood. 
“Whoever does you a favour” means, whoever treats you kindly in word or deed. 
“Respond in kind” means, treat him kindly just as he has treated you kindly. 
“If you cannot find the means of doing so” means if you do not have the money. 
“Until you think that you have responded in kind” means, repeat the du’aa’ until you think that you have given him his due. 
One of the du’aa’s that you can say is Jazaak Allahu khayran (may Allah reward you with good). Al-Tirmidhi (2035) narrated that Usaamah ibn Zayd said: The Messenger of Allah (peace and blessings of Allah be upon him) said: “Whoever has a favour done for him and says Jazaak Allahu khayran (may Allah reward you with good) has done his utmost to thank him.” Narrated by al-Tirmidhi, 2035; classed as saheeh by al-Albani in Saheeh al-Tirmidhi. 
“Done his utmost to thank him” means, he has done his utmost to express his thanks, because he has acknowledged his shortcomings and that he is unable to reward him and thank him, so he refers the matter to Allah, that He might reward him in the best manner. One of them said: If you are unable to give him back in kind, then speak at length thanking him and making du’aa’ for him. From Tuhfat al-Ahwadhi. 
The Standing Committee was asked a similar question, and replied as follows: 
There is nothing wrong with accepting it (an amount of money as a gift), without you longing for that, and you can respond in kind if you are able to with an appropriate gift, or you can make du’aa’ for him, because the Prophet (peace and blessings of Allah be upon him) said: “Whoever does you a favour, respond in kind, and if you cannot find the means of doing so, then keep praying for him until you think that you have responded in kind.”   Narrated by Abu Dawood and al-Nasaa’i. 
Fatawa al-Lajnah al-Daa’imah, 16/171 
And Allah knows best.