Without additional detail on your indirect budget needs, it is not straightforward to give advice in this case. The standard indirect cost rate of 50% is the most common way of requesting indirects. If that would be too much for your needs, you can always opt for a lower rate (e.g. 30%) so you free up some extra funds for other costs on the proposal. However, going for an indirect cost rate that is higher than 50% will likely trigger a rate negotiation at time of award.