Having lived long enough to remember the years before these products were available, I can tell you ... there's a reason we're willing to pay as much as we are for them.
I use a feed-through product (I forget the brand name) on my dog, for fleas and ticks. I do not give it to him monthly because in my experience, I do not need to. I give it to him and then, when I notice a live tick on him that's not dessicated/dead (which seems to be what the meds achieve), I give him another. This frequency (which seems to work out to every other month or 3rd month) seems to work for us. I do give him one at the start of tick season, for sure, for obvious reasons.
When I don't need tick protections (around where I live, ticks are pretty seasonal, fleas not as much) I use Comfortis, which is only good for fleas (also feed-through) but may be cheaper (it's been a long time since I bought any, so not sure). Again, it's a more every-other or every-3rd month kind of dosing. I don't know how big a problem ticks are where you live or whether you plan to let your dog run places where they are found (versus being in more of a city environment); you may decide you don't need tick prevention at all.
We don't have much carpet in our home, so the risk of a systematic flea infestation is small. If we did, I might use a more enthusiastic scheduling strategy.
I'm not willing to use the apply-to-skin (as opposed to feed-to-dog) products because I have a kid in my household and don't want him exposed to the chemicals from the dog's coat. But you may feel differently, and the apply-to-skin stuff may be cheaper.