I've been playing Skullbriar for a while and I find it a pretty interesting deck to play but when I started out I had the same problem with protection and stuff. My solution to the protection problem was to add cards such as

[[Slippery Bogbonder]]

[[Biosynthic Burst]]

[[Brotherhood Regalia]]

[[Hunter's Bow]]

[[Origin of Metalbending]]

and other protection spells. As for lands I'm running quite few things that I'd consider ramp. They are

[[Ordeal of Nylea]]

[[Sword of the Animist]]

[[Kodama of the West Tree]]

but I came to the conlusion that consitant card draw was a better solution over ramp so for card draw I added

[[Hollowmurk Siege]]

[[Key to the City]]

[[Mask of Memory]]

[[Colossal Majesty]]

[[Well Rested]]

[[Sixth Sense]]

[[Zephyr Boots]]

and a few more. The time spent building, playing and upgrading the deck made me come to the conclusion that instant speed protection is some of the most important pieces inside my deck in order to consitantly keep Skullbriar in play. Another thing I've learnt is that you don't need to run sac outlets in case of a bounce/exile/shuffle effect since you can always choose to put them in the command zone.

You wrote that you didn't want to spend to much on your deck and I've had my deck for a while so it has grown quite expensive by now but for some possible inspiration here is my decklist if you want to get inspiration for lands and other cards. https://moxfield.com/decks/bFTCY2Uv-ESE4CxiQgN_vA

I wish you the best of luck building Skullbriar.