As well as joining the group on rambles, you may want to plan your own walk in the forest. These are the resources members use most.
The 5th edition is 17 walks with sketch maps, written by members of the group.
The 1:25 000 map of the New Forest, available from bookshops.
The Christchurch to Lyndhurst road is busy, so it pays to pick a good crossing. For walks that cross between Bank and Wilverley Post, a35crossings.wordpress.com has the map, photos, and notes on stiles and gates.
All of them suit an independent walker; the smaller ones do not have enough space for a group. Forestry England charges for parking. See also Forestry England parking information.