First off, sleeving your card IS a MUST. However you CAN do it on a budget! Check out sof penny sleeves by ultra pro, they are not as durable as some, but they get job done and man are they
sleek.
There are cheaper deck boxes you can buy, however if you've ever made anything out of duct tape, you'll want to go for that. I had a duct tape deck box for about a year before I got a nice ultra pro suet tower, a cheap, but quality, deckbox.
Mats are going to be expensive, straight up, don't know what to tell you.
And finally, you are playing standard and that's fine, in order to compete and save money, I would suggest going on youtube to the channels [The Mana Source], [Tolarian Community College], and [Mtg Degree] for free tips on playing at the top of your game. As well as this, many of these channels provide budget deck lists for any format.
PS look on deckstats for lists with the "budget" tag.
PSS PLAY PAUPER-
https://www.reddit.com/r/Pauper/