Wool X3 !
Best thing you can buy and the best way to stay warm is to create your wool layering system. This starts with the base layer and may be the most expensive of all. As Joe says above, "Merino wool sweaters from Goodwill and Army surplus pants are cheap layers " You can find Asbell pullovers pretty cheap too.
Several brands of wool base layers out there... Cabelas, Ullfrotte' Smartwool, Minus 33, First Lite, etc, etc. A Top and Bottom may cost you between $150-200 but it will last you forever with a little care and you will thank us later ! We have never been warmer since we bit the bullet about 5 years ago and bought our Ullfrotte' base layers in 400gr thickness. Simply cannot hunt without it now. Plan on buying some Minus 33 170gr thickness this year for early season and to compare with our Ullfrotte'. JMHO