Ramunap Excavator is a good investment for $5- $6.
To keep the deck within budget, a few good options to consider
- llanowar elves because why not
- dwarven miner gives you additional targeted land destruction
- rampant growth and farseek are both 2 mana ramp cards that take lands out of your deck.
- open the gates is a one mana basic land (or gate) fetch.
- sylvan scrying grabs ANY land for 2 mana
- reap and sow, journey of discovery and if you want to put the extra money in you can go with cultivate and kodama's reach
- something like a skyshroud ranger or arboreal grazer to play extra lands
- explore is a 2 mana card draw with a free land drop
- mending of dominaria (i think it's called) is an inexpensive mass land recovery card.
- nylea's intervention is an X spell to remove lands from your deck and put them in your hand, OR you can use it to destroy flyers.  This card is still inexpensive but I think it will go up.
- if you have a sasaya, orochi ascendant then i would pick up a nylea's intervention and throw both of those in.
- desolation is an old visions enchantment that never got reprinted and I think everyone just forgot about it because it is such a natural fit and somehow still costs less than $1.  It should be a $4-$5 uncommon by now.
- don't be afraid to take the land count with windgrace over 40, especially when using mass land sac.  Lands are weapon with landfall and mass destruction and swift recovery from a board wipe


Windgrace is an extremely powerful deck and will serve you well why frustrating your opponents.  Check mine out.  I have lots of options available for trade if you want to have a look.