The sociology of dowry in India is not within the scope of Law SE, but we can say what the law is. The Dowry Prohibition Act, 1961 penalizes anyone who "gives or takes or abets the giving or taking of dowry". Ancillary laws were enacted to prohibit act thought to relate to dowry, such as beating up your wife (IPC 498a) which are not just about dowry but which have a connection to dowry.
'Dowry' is
any property or valuable security given or agreed to be given either
directly or indirectly:
by one party to a marriage to the other party to the marriage; or
by the parents of either party to a marriage or by any other person,
to either party to the marriage or to any other person;at or before or
any time after the marriage in connection with the marriage of said
parties but does not include dower or mahr in the case of persons to
whom the Muslim Personal Law (Shariat) applies.
An important exception is that
(2)Nothing in sub-section (1) shall apply to or, in relation to,-
presents which are given at the time of a marriage to the bride
(without any demand having been made in that behalf): Provided that
such presents are entered in list maintained in accordance with rule
made under this Act;
presents which are given at the time of marriage to the bridegroom
(without any demand having been made in that behalf): Provided that
such presents are entered in a list maintained in accordance with
rules made under this Act; Provided further that where such presents
are made by or on behalf of the bride or any person related to the
bride, such presents are of a customary nature and the value thereof
is not excessive having regard to the financial status of the person
by whom, or on whose behalf, such presents are given.
That is, it is not illegal to give gifts.