stable - 'affordable' tripod....

looking for advise...

i think i need a more stable tripod...

i have a manfrotto neotec tripod that seems very useful in certain circumstances...

it is very easy and quick to deploy - can set it up with one hand if i am twisted ofer a tree in a swamp of bog... lots of plusses....

but, i can 'clearly' see however, that i need a more stable tripod for some of the things i wish to do...

i am using an acratec gp-s ballhead...

and simply cannot afford an expensive rss or other 800.00+ unit... (aarraugh...)

what are folks using and finding acceptable with d800 and up to 300mm lens combos

many thanks

p.