Need help with resources

Ok, so already, I'd say you have a pretty fantastic starting roster of servants! Obviously, you'll want to be using Alterra as your main saber, because she is the best 5-star saber in the game that is not limited-time. She works well with most team set-ups, with her qaabb deck. She has a very vanilla style of play, and she's simple to use. For your lancer, I definitely recommend using Culancer over Elizabeth. He has amazing endurance, and he's pretty synergistic with most teams. As for your archer, it seems Kid Gil is your only option for now, (I don't really consider David to be someone worth investing in. He's just so bland.) and he's not too bad, but if you want to wait until you roll a different archer to spent experience cards on, that wouldn't be a bad idea, as you could just fill your archer needs with support servants until then. Now, for the rider class slot: You have 3 very good riders, so it's really all about preference. Ushi is great for quick teams, so her deck works well with Culancer's. Martha has nice healing capabilities, and also has 3 arts cards, so definitely level her up the most if you want an arts-based deck. FInally, your highest-star rider, Iskandar, is very offensive, with 3 buster cards, so if you want an all-around powerful servant, who you can add to a buster-based team, choose him. Overall, though, you have some really good riders. Ushi and Martha are totally cute too, and they're even drawn by the same artist, coincidentally. Iskandar is super meaty and buff, and has a great personality. So it's totally up to your preference for which rider you want to mainly use. For your assassin, I'd say definitley leave Stheno out, as she's really not that great. Her niche is only useful in very specific cases, and her attack id pretty low. Plus, just between you and me, I really don't like the style of art she's drawn in. I would describe it as "scritchy and scratchy." That leaves you with the choices of either Jekyl or Hundred Personas. Either one is alright, I suppose. I would choose Jekyl if you want an offensive team, and Hassan if you want a quick team. Other than those two, you could just wait for the summer event that's coming, where you can get a free welfare Scathach assassin, who's really useful, and totally gorgeous. Next up is your caster. I would forget about Cucaster, as he's just really lackluster in every way. That leaves you with Nursery Rhyme, who's pretty good, I'd say. She has some good self-buffing abilities, so that makes her pretty durable and surprisingly offensive, and she has 3 arts cards, so she's good at firing off her NP, and can fit well with any art-based team. Last but not least, we have the berserker spot. The answer is simple: Lancelot. He's a great berserker, with 3 buster cards, so he can unleash buster-brave chains, as well as fit into decks well that include your Iskandar and Alterra. He also has a Quick NP, so he can do well with Ushi and Cu, as well. So there you go! I hope I was able to help, and let me know if you have any other questions!

Meteor horseshoes are pretty rare i think, i have had trouble farming them as well as hearing other people saying the drop rate sucks. Aside from events that is.
I can agree with what Nolan says. i would use Lancelot for farming hands/dailies and Beowulf for bosses maybe since he has guts and Lancelot doesn't. I usually have a difficult time keeping Lancelot alive.
You don't have to focus solely on the good servants. This game is totally playable with bronze servants. I saw someone beat the Lourve mission with bronze servants.
But to add on to Meteor Horseshoes, use the sites planner to figure out what you need and maybe read about some of the materials. I find things like Serpent Eye's are easier to obtain tenfold then compared to Meteor Horseshoes.
Also don't be like me and think 100 million QP is a lot, when i first started i was thinking like why do people keep saying 200 million qp is not enough. But when you start leveling skills past 6+ you'll know why.