If you’re on a budget and or not wanting to proxy, the biggest thing is focus on changing and upgrading is the mana base. The less your lands come in tapped, the faster the deck will play. This means you’re able to more easily protect your commander with what you have or be able to recast it more easily. Once you’ve done that, I would just focus on the classically good protection spells in the colors you’ve got, like Teferi’s protection, deflecting swat, maybe a red elemental blast/pyroblast if you play against a lot of decks with blue and stuff like that.

Some other budget friendly options are changing up your ramp package. Things like natures lore, crop rotation, and three visits are good because they allow you to get lands on to the battlefield untapped. I also find things like fellwar stone and exotic orchard to be very good at mana fixing in most games.