You should always make a starter with liquid yeast as the smack packs only have enough yeast to properly pitch into 2-3 gallons of beer. Sure it will still work eventually and usually make decent beer but underpitching will create slight off flavors and making a starter will just give you a cleaner tasting, better beer overall.
Starters are not difficult and don't have to require a stir plate (but it certainly helps). All you need to get into starter making is a growler or similar container that can hold at least a half gallon (Carlo Rossi wine jugs are a gallon and its only about $10 with the crappy wine if you want it). Then you just need some aluminum foil for the top and a pot with a lid for boiling your starter wort. It takes about twice as long and you get less yeast without a stir plate but it will still work and boost your yeast cell count so you get a proper pitch.
If you don't want to bother with starters then I would suggest using dry yeast instead because they have enough yeast in a pack for 5 gallons when you properly rehydrate in water (viability drops to about 50% when pitched in wort). You can usually find a dry yeast that can substitute for the yeast in most recipes. Us-05 is the same as 1056 and wlp001 and great for American ales, s-04 or Nottingham is good for English or Irish styles, you can also get dry yeast for Belgian and saison beers. If you have a local homebrew shop I would suggest getting some dry yeast for this upcoming brew instead of pitching that smack pack that may end up being a dud.