Is this a standard deck? I’m kind of assuming standard instead of block because of the Lightning Bolts and no significantly older cards.
I’m not a fan of Seer’s Sundial. I’d rather have something which I can use to draw cards on the opponent’s turn instead of my own. If I draw something I want to play I want to be able to do that, and even though it’s one of the lowest usage cost versions of the tome, I’m not impressed with the casting cost. If this is a beatdown deck, and it certainly seems to be so, you want to have things which help beat down.
Also, were you misremembering Borderland Ranger? It’s a 2/2 for 2G, not GG, which lets you put the land into your hand, so it doesn’t allow double-landfall trigger, it just helps you get land into your hand.
Things I’d consider for a landfall deck in G/R
Harrow - almost a must really, much better than the Khalni Heart Expedition, mostly because you can sacrifice a tapped land and get two untapped.
Plated Geopode - first strike is not an evasion ability but it is a strong enough ability, combined with instant speed land fetching via Harrow or a fetchland.
Jund and Naya Panoramas fit the bill here, and don’t sacrifice the tempo as much as Terramorphic Expanse, IME, it’s worth testing for your build. Getting a point of mana without spending a point can be good with a beatdown deck, but if your opening hand is two lands, wouldn’t you rather they both be capable of producing mana? This leaves you the flexibility to crack the land for landfall on their turn or use it for mana yourself.
Firewild Borderpost - Nice landfall enabler and accelerates you a bit, squeezing every last land drop out of a deck with no more than the average number of lands.
Searing Blaze - Makes your mana balance a bit harder, but the extra damage can be very nice, since your deck is mostly concerned with getting damage through.
Toxic Iguanar - is an often overlooked card which gets a lot better in a R/G deck and can hold the ground a lot on its own.
Vines of Vastwood - Since your beatdown creature is going to be free(and very vulnerable), why not spend GG to give it +4/+4 and the good half of shroud? All around versatility is good here too.
Electropotence - Like Vines, it can take advantage of the fact that your mana is not all tied up when your beatdown hits the board. It stretches the damage your temporary critters can do to either clear the way, or just smash face. It’s more mana intensive and slower than Vines though it can clearly generate more damage over time although it can’t save critters from targeted kill like Vines can.
Windstorm, Deadly Recluse, Ember Weaver, or some way to deal with flyers should probably be in your sideboard at least, depending on your local metagame.
Naturalize - I’m a control player at heart and I feel naked with no way of handling artifacts and/or enchantments, but if you’re comfortable doing so, freak freely.
River Boa or Mire Boa - Depending on your personal preference, gives you a regenerating defender or an aggressive evasion creature depending on how the game goes.
Branching Bolt - Probably worth testing if your games go on for a while. If you just run people over with the Zektar Shrine Expeditions then it’s not a big deal, but it’s one of the better new bolts.
Volcanic Fallout - Leaves more room for the big ones to fight in, you know. Hilarious with a Bloodbraid Elf on the stack.
Here are some more expensive suggestions.
Scute Mob - If you’re worried about your late game power, this guy is essentially a 5/5 for 1 after a few turns. Especially if you keep the other land-based accelerators like the Borderland Ranger.
Birds of Paradise - almost always a worthy addition to any multi-color deck which can reliably produce G on turn 1.
Lotus Cobra - The jury is generally still out on this one. It looked all cool and flashy when it came out, and my shiny foil one made me smile when I opened it, but as a way of reliably squeezing extra mana out of a deck I haven’t been that impressed. On the other hand, he essentially makes cracking a Panorama free, makes a Terramorphic Expanse produce two mana if you crack it as soon as you play it, has great synergy with Harrow, and has a lot of other cool effects on a deck with low mana requirements. Basically the dream deck for this card seems to be close to what you want to have. Probably worth testing, but don’t sink cash into them until you’ve tested with proxies is my recommendation.
Strength of the Tajuru - In a deck which can generate lots of mana and has creature-based damage is just a huge beating and can virtually cinch up a late game.
Comet Storm - if you find yourself frustrated by blockers a lot.
Omnath, Locus of Mana - is kind of stupidly good if you can swing it. If you decide to invest in this guy and play him, the best advice I can give you is to find some way of tracking the mana in your pool because you will need to know a lot. We’ve been using dice.
Garruk Wildspeaker - more for the longer game than anything else, but certainly good.
Sarkhan Vol - Better than Garruk probably.
Ok, that’s probably enough for now. 
Enjoy,
Steven