This is what I learnt from the teachings:
It is not compulsory for Christians to make vow, but when you make a vow to God you must fulfill it, you can make different vows to God for example you can say you will never commit sin anymore and this kind of vow you must fulfill it as a believer of the word of God. When you make vow to God and you fulfill the promise made to him, God will be happy with you.
The doctrines of God said we should always give, we should give according to our power. We should not allow any man of God to force us to give what we don't have. Some churches do tell their members to always pledge, they tell them to pay for church building, to pay for new bus, to pay a contribution towards envagelism whereas God says we should not force our followers to do all these things. In the bible God commanded us that we should not give what we don't have. The contribution in the church should be a voluntary task not forcing member to give. The members are the one to decide what to give not forcing them to give. Boxes are always everywhere in the church for you to drop your contribution, not the church bringing the box to you. Some churches do bring the contribution box to their members, this is not proper in the eyes of God.
God loves a cheerful giver. If you always give God will love you. You don't have to collect money from your members in all your gatherings. Giving to the church should be voluntary. David offer thanksgiving as a vow before his people. You are not stealing if you don't pay your tithes because elders in the church of God does not have the right to command you to pay tithes.